I feel like the general consumer doesn't even know it exists. I wonder if your friend had known about it if you didn't mention it to him so many times.
This is the same for PSNow. You mention that you can play/stream over 600 PS2, PS3 and PS4 games on PC and a lot of people won't know you can do this. But I don't feel Sony have advertised it that much outside of gaming communities.
Game Pass is good value for those that are more inclined to play many games and over the year may spend a lot on games, so getting many to play is great for them. Not for me however, I'm not a big spender on games so it's point is kinda missed on me.