This thread really made me question myself: "Yeah, why am I actually playing Pen&Paper?"
I voted for social and co-op, but I feel this doesn't fully express my thoughts.
I think Pen&Paper is the much better alternative to MMORPGs. I used to play MMORPGs a lot and had some huge fun. I didn't play so much with friends, but I found new friends in the game and playing together in co-op and getting to know each other better was really great. Something I can't really do in real life (too shy and I feel in real life people are not very fond of you just talking to them when they don't know you yet).
I played one MMORPG for over 10 years, but the community slowly died out and I tried to find a replacement MMORPG but just couldn't really enjoy any I tried. Eventually it felt like all of them were the same. Way too linear, too repetitive, too much grinding and most people focusing on competetive aspects over role-playing (really, it feels like 98% of MMORPG players only play for PVP and really only do PVE to be stronger for PVP). It honestly started to become really hard just to find someone to party up with.
Pen&Paper solved that problem. Here, you have a lot of freedom, it doesn't feel repetitive at all, there's no need to grind and all players are fond of playing together co-op.
Now, I'm actually only playing online and I'm a DM and I might question why I'm doing that. Well, the problem I was facing was that I'm quite strict when it comes to rules as I'm coming from a video game background. House-rules are like a no-go for me and I really only wanted to play the officially released adventure paths, but in the end I felt like I couldn't find a DM that really could offer what I'm seeking, so I decided to DM myself.
That's a lot of work and you don't actually really get to play the game as a player, but that was fine for me. Honestly, even as a DM I still feel like a player as I'm still following the adventure paths very strictly and don't read too much ahead. Plus you still have the excitement of not knowing what your players are going to do.
So, I play by post daily and there are days where I don't really enjoy it too much. Maybe work was hard and there's a lot to do at home as well, so I'm exhausted and don't want to do all those dice rolls and think up all those things, but I keep pushing myself. And it's still rewarding because you know your players are having fun and appreciate the work you put into it (especially if you are still around years later - most play-by-post groups never complete an adventure because of disappearing DMs).
Plus those are only some days. There are other days where I'm really excited to do the next post. Or days where I'm simply bored and demotivated to do anything, but I'm still good to do another Pen&Paper post. It feels like it's that one thing I can always muster up the motivation to do.
Talking about motivation, I'm actually also a game developer and being a DM is kind of similar to developing a game. At least part of it. But I often have motivational trouble when it comes to game development. I hardly ever am able to force myself to start coding (and I'm even less motivation to do graphics and music), because I'm only really enjoying some aspects of the game development process. With Pen&Paper, it seems to be much easier to motivate myself to proceed with the story. Maybe because it's in smaller bits or includes more of the parts I enjoy than those I don't enjoy.
But I think a very big factor is the social aspect here again. If you just develop a game alone, you have nobody actually caring about it. Nobody knows you're making a game, nobody helps you making the game, nobody cares about your game until you release it. With Pen&Paper the players care about your game from day one because they are already playing it.
So yeah, I guess that's all.