Because SWG as a game was missing a lot of things too. I will never say SWG was perfect. But some elements of it was pretty good.
Bad:
The macro-ish combat system where you could script your combat sequence on 1 key was horrible.
The lack of content (quest)on the ground and in the space.
Those 2 things killed SWG for a lot of people. Even more when WoW came out and offered a lot of content from lvl 1-60.
Nevertheless, crafting, guild city, merchand, player housing was superior to all other MMO i have played. Those are the elements i would love to have in sw:tor.