The thing is that the two finesse longswords are only finesse because they're connected to Corellon Larethian ([Larethian's Wrath]) and Eilistraee ([Phalar Aluve]), who as Elven deities are exquisitely graceful with their blades that it ends up looking like a dance.
So although any regular Joe can swing a longsword, they would be doing it brutishly/crudely without any grace, which is why these are the only two finesse longswords (to illustrate elven grace).