Some people need to learn their history a bit better. France was actually the biggest proponent of using DC instead of Greenwich as a baseline. They pushed for it hard after they realized Paris would certainly lose out. If I have to explain why they would have done that, then you REALLY need to learn your history.
Washington DC was never a practical choice, and not just because Greenwich was already in such common use. A DC based system would have put the international dateline somewhere absolutely obscene (I forget exactly where).
Also, I'm pretty sure a dim American like me isn't supposed to be able to keep up with Europeans in understanding irony. Strange then that some of you are making cracks about arrogance while talking about an Uber Time Zone, as if there is any such thing. People in the US and Canada generally use the much more convenient EST as their point of reference. Europeans I think generally use the (for them) more convenient GMT. Everyone else uses whatever is convenient locally. Savvy internet users really ought to be familiar with GMT, but the idea that it requires a great deal of ignorance for someone outside of Europe to be unaware of it is silly. It is just not used nearly as frequently as some of you seem to think. I would wager that more people know the time difference to either New York or Hong Kong than know the time difference to Greenwich.
I should be clear that I understand what GMT is. It doesn't throw me THAT much, and I don't have any problem with GOG using it. I will say that they should probably include EST as well, given that so many of their customers are far more accustomed to making conversions based on that. As has been mentioned, GOG press releases often fall a bit short of the idiot-proof simplicity that you want from that kind of writing. My English comprehension is very strong, and I still sometimes have to reread them to be clear on exactly what is being said.
Bottom line: it doesn't take THAT much ignorance to misread a GOG press release. People saying otherwise should be careful about accusations of arrogance. Having said all that.... If you didn't know what GMT was, you really should have looked it up :).