Telika: Nope, I buy many games just for that. Knowing I won't re-play them, but paying a debt, even at a symbolic level. It's not only about GOG, but also other games, movies, comics, CDs...
The problem is, when we're at the most "playing" age, we usually don't have the means to get our games legally. So, we kinda accumulate moral debts, by "stealing" what we would not have been able to buy. And, well, afterwards, it's a bit too late to set it right. Even if you overcome your disinterest, the compensations are usually futile (what does gog offer to the original authors -when anything at all- compared to what they would have got when support was crucial ?).
So yes, to clear conscience. We do. It doesn't work that much, but, we have the "at least" to hold onto. :-/
I had a really nicely put answer ready, then I read Telika's...