What games are missing.

Why can't I play the same game on more than one PC? What I mean is why can't I continue the same game on ANY PC that has the game installed. If I install a game at home and am working my way through it why can't I install it at work or anywhere else and continue the same saved game there, keeping the two versions synced to each other? There has been the occasional game that offered an import/export saved game feature or other games that allowed for the moving of saved games just by copying the save game files around but none of these is a REAL solution, webspace is cheap, saved games are small... why can't I use something like gmail's gig of space to store saved games that I could access from wherever?