Guild Wars 2

“Because it is a MMO” is not really an answer.
“MMO” means Massively Multiplayer Online and in no place it includes that you have to team with the other players to play. You are playing with them in many other ways than going to a dungeon or grouping in a zone.

The “forced grouping” comes from early development of MMOs (and before that of MUDs) but it is changing since each time more people wants/needs solo play inside a MMO.

Most games cater to the “solo play experience” (as GW2) during gameplay and then forget about it at end game. Doing this causes many people stop playing a game they like (or even Love) and change to a different game.

Many intelligent developers realize that they are losing customers and develop additional interesting things to do at level cap for “solo play” or non committed grouping (so that you can enter or leave as you need). GW2 is one of these games and people rightly demand ANet to keep it the same way for future development.

Why do people play solo or do not want to commit to long groups?

There are many reasons and some are temporary while others are permanent, for example:

. Lack of time investment. (Many people needs to leave without notice, try to do this while a dungeon run).

. Desire to experience content at their own speed. (Tried to follow story in a dungeon run while other people are rushing it).

. Desire to avoid playing with rude people. (Have anytime played with a know-it-all player that tries to force other players to play as he sees fit).

Refusing to cater for the “solo play experience” only reduces the number of people playing while developers want to increase the numbers.

My perfect MMO would have a solo player copy of each dungeon (with lower rewards to incentive group play) and dedicated repeteable content for solo players at end game with different selectable difficulties.
Also there would be comparable rewards for solo play and gorup play, with solo ones being slightly lower (between 5% and 10% maximum) or different (for example oriented more to survivavility than damage) and taking longer to attain.