Probably because TOR is KOTOR 3, 4, 5, 6 etc. It has more content than all Bioware games to date.
That's the joy of an MMO, you don't really need another game because you can update the current one. I doubt I'd buy a Bethesda MMO however. While I love the style for their single player RPGs, I much prefer the themepark style for MMOs.
