Weapon Finesse has two niche's.
1. For builds that favor/benefit from high AC/Reflex saves. A MAD class like monk makes a good example, since wind stance is so nice for faster attacks and doublestrike; you retain high reflex saves, high ac, while losing a small amount of damage, at the cost of a feat. Classes that rely on 'rider damage' such as sneak attack damage, or bursting rings in the case of the monk, are options as the loss of damage due to lower strength isn't as steep.
2. 28 point builds with races that have a dex bonus: with finesse you can attain respectable hit modifiers while still having points left over for Con/Str/Secondary stats. Elf/Drow Elf/Halfling fall into this category; starting with a 16 dex costs the same as 14 str, and requires no tomes at all to qualify for the TWF chain.