Flaws and strengths sections on NSes are only necessary on stat-driven NRPs, but even that's up for debate considering a stat-driven NRP keeps the player factions in check by using well-defined formulas and numerical values. The only thing that has ever come out of a F&S section on a NS skeleton are people coming up with completely illogical pros and cons for their nation that they aren't going to stick to when it comes to IC interactions in the first place. They're pointless in character sheets as well, because well-written characters will have strengths and weaknesses interwoven into their personality, skills and inherent traits.

And no, they don't help with diversty. Diversty happens when people don't try and rehash tired ideas and concepts that are ingrained within traditional Tolkien-esque fantasy settings---like Aryan elves, metal-loving dwarves and socially-awkward gnomes that have a sexual fascination with bombs and all things machinery.