Assuming that the number of non-Galaxy users is far smaller than the number that use it... why the hell would they care about proving it?

Where is the proof that number of non-galaxy users is smaller? On what facts is the assumption based?

On the statement you made in the above post where I quoted you.

There might be a miscommunication...Gog is the one that keeps saying soooo many people wanted a client. I'm saying I don't believe them. If they know so many want and use galaxy then they should be able to show the numbers, steam can and does. And like I said to Adaliabooks "after some of the things they've done over the last few years is exactly why I don't take them at their word". If they are telling the truth then they should be willing and able to back-up their claim with real numbers instead of self-serving statements.

Thing is, if the majority of people don't want a client and GOG knows this - it's absolutely insane to go ahead with it, pouring resources into development, heavily advertising it, tying their bread-and-butter CCG to it, and pissing off the majority of their customers by going ahead with it. It makes zero sense. And I know they've done some bizarre things in the past, but this goes beyond the pale. You don't piss off the majority of your customer base, especially when that customer base has grown exponentially in the past few years. You cater to them.

So what? GOG doesn't. It's not the way they want to do things.

And that's fine: you don't believe them. Others don't believe them. But, GOG's not going to tell you, them, or us the numbers. And the only logical conclusion to that behaviour is that the people that don't want the client (and are therefore looking for 'proof' that it's desired) are such a small minority that catering or not catering to them doesn't really matter.

LOLWut? The stuff I do costs hundreds of thousands of Euro in development...

Well it would prove X number of people are using Galaxy regularly. Given that Galaxy is currently optional in all but a few edge cases that proves that X number of people are choosing to use Galaxy, presumably because they like it and find it useful.
If you don't accept that as proof that Galaxy is desired by people then you won't except anything as proof and the whole discussion is moot as you are just burying your head in the sand and pretending things are the way you would like them to be...

So answer me this... if no one is really using Galaxy, no one asked for it in the first place and it doesn't make GOG's lives any easier (in fact it makes them worse as presumably everyone is sending support tickets complaining about Galaxy installers etc.), then why are they still spending millions developing it? Why are they still pushing it?
I know you mentioned before how it can be hard to admit something is a failure, but I doubt the people at the top can't see the statistics and know it's all a waste of time and money if that were the case. If adoption is really as low as you assume four years after it was first available and everyone is shouting and clamouring for 'the old way' then why are they still hiring new developers and spending money on it?

As I pointed out before https://www.gog.com/forum/general/if_gog_isnt_going_down_the_drm_route/post114

Those who want to believe whatever gog tells them aren't going to change their minds and I won't change mine without actual proof. Also as I said before, I'm tired of wasting my time.

Fair enough, and I'll just say this one last thing: I accept that no one's going to convince you (that much you've made obvious), but if you think GOG is going to provide 'proof' that the majority of their user base wants something like Galaxy, you're not going to get it. They don't provide numbers to us; they never have. They don't need to. It's not like their business is hinging on proving to you or other people that don't want Galaxy or that believe it's just a step towards DRM that what GOG's doing is because of metrics they've gathered. And seriously, at this point I wonder if you'd even believe the numbers if they provided them anyway.

Seems like everyone here will just have to agree to disagree. I'm sorry you feel that GOG is jerking your chain for the sake of it (else why would they?) but it is what it is.

If something is happening, and it doesn't make sense, my old man always told me... Follow the money. Someone is making a buck somewhere if it seems stupid that something is happening.

So anecdotal exceptions disprove general rules? ;p

And a million Euros is pocket change these days -- though dollars are even worse, I imagine.

Another possibility is that the majority are ambivalent re proprietary clients, and GOG figures it can get away with gradually making Galaxy mandatory, partly by refusing to fully support the offline installers -- and it probably can.

But why?
In this scenario GOG is the big bad slowly sneaking a client in and then making it mandatory. What do they gain by doing so?
Sure, Galaxy is supposed to be easier for devs to deal with and less actual human oversight is required on GOG's part, but I'd hardly call that worth the millions spent on it and the risk of putting off most of their customers (who apparently don't want it).

So what do GOG stand to gain by spending four years making a client nobody wants and then forcing it on everyone until it is the only option to get access to you games? What is the business advantage they gain?

Is it like Microsoft developping and selling Zune or their Windows Phones? They wouldn‘t develop them if there was not a big demand for it. Oh wait ...

Ambivalence means having mixed feelings about something, so I'm not assuming that nobody wants Galaxy; in fact, I assume that a considerable number of peeps are somewhat open to it. I would be, too, if it was open source.

As for why, open your eyes and look around you. What do you see Microsoft doing? Or Google? Or Steam?