you guys, srsly, you must be kidding. the batsymbols are meant to be an extension of who batman is, not for realistic purposes. "why have fins?" is like asking why did batman have to make bat-shaped throwing devices and call them "baterangs"? batman is a nutjob, almost EVERYTHING he has in the comics has a batsymbol. its meant to show ppl that batman is comin for ya, not "oh, that tank thing is comin". oh brother. there is a reason why the B89 batmobile is still considered the best batmobile, aesthetically. it is a BAT mobile. when someone sees it, they know its batman. its been with the character as long as joker has had permawhite skin. nolan changed both those things, and i dont agree with it because aesthetically, they both look like sh** in the end. there are some things you just dont mess with, and 2 of those things are batmobile and the joker. you just....dont mess with those things.
i find it funny, the ppl who b itch the most about comic accuracy are the ppl who are saying "tank-lookin batmobile and non-permawhite joker ROX!!". kinda ironic huh?