At sometime you come to a point where you feel you have accomplished everything, or have you? Another time, you just want your PC be a particular spot and enjoy the environment. This topic is mainly what keeps your PC going and not give up the game or have to create a new character.
For me, just hanging around heart of Boston has me going with a 100+ level PC. The wars between factions, enjoying a Mutant Suicider or two blowing up things up that does not involve my PC, and, if that is far enough, the BOS joining in, makes me love the game.
The story itself is subpar (for me since TES III is my benchmark game for Bethesda game pinnacle), but what Bethesda lacks since then, the environment, wandering (forget quests given to you, just be a wanderlust) this game is golden.
Thus the reason for this thread, what keeps you going to play the game? For me, what Bethesda does right, is the environment of random encounters and locations themselves. Wish the story writing is better, but they excel in wandering enough and either chaos is nearby or something else (a new dog, a new quest, or just meeting new NPCs [wish they fix the potential new random encounters vendors, level 4 as they do not show up, yet population count says they are there???
Ultimately, I just love wandering around Boston itself, and just enjoy other factions battles and join after is one is victor and put that one down, unless an ally. For anyone else, what about you?