because some of us enjoy it?
anyway, it did have the same story, ME. a hero jedi/spectre goes far-far away pursuing his duty only to find an ancient evil, which transforms him, he then goes rogue. a newbie spectre/jedi is tasked with eliminating the new enemy. then he destroys some derelict ship and saves the day, woohoo.
how is it not the same? the only major difference was the plot twist in KOTOR with the rogue jedi and the newbie jedi being the same person. that only proves KOTOR's plot had a lot more to offer. ME is more straight-forward and simplistic. in terms of gameplay they don't differ much either. KOTOR is focused on lightsaber battles, obviously making it a FPS would just over-complicate things.
now, ME2 utilized a slightly different formula, it definately was an improvement design-wise. the plot, however, leaves a lot to be desired