I mean the personal skills that some characters comes with add something to the characters and their personalities.
It is something that came to my mind while playing the games this time. I don't know if it was intentional that the devs did this, but it makes the characters more interesting to me.
For example, Mia's Vantage because she is fast. Tormod's Celebrity because he was raised with Laguz and moves a lot. Mist's Miracle because she is lucky and maybe because of the medallion. Keiran's Gamble seems to fit him, he looks like a guy who might goes for a stronger attack (critical) and risk missing.
The biggest example is Ilyana. She goes unnoticed so she gets the Shade ability. Since she goes unnoticed because of her Shade ability, that makes her less experienced than the rest of the Greil Mercenaries to the point of still being a tier 1 character.