Except stuff doesn't work that way for several reasons.I'll counter that you have no guarantee that it won't work out. If character A pays low price for combat stuff and high price for investigative stuff while character B pays high price for combat stuff and low price for investigative stuff, you'll most likely see A with mostly combat abilities but a smattering of investigative stuff, while B does the opposite. The imbalance you suggest only occurs if one character takes only the inexpensive options while the other does the opposite and overindulges in expensive purchases. In any case, getting agency over the game is only going to mean dealing with what the GM puts in front of the characters, and most GMs will adjust adventures to the characters that are active in them.
For example, some activities(like combat) benefit from the whole group contributing (if the 'good at combat' guy doesn't single-handedly destroy encounters, he will benefit from the input of every 'average at combat' guy, as every added damage helps the combat end faster). Other activities (like social stuff) only involve thre most competent character (apart from some very special circumstances there's little reason to not let the party face do the talking). A good at social/average at combat character will get drqstically more spotlight time than an average at social/good at combat one.
Your experiences are not universal. The group doesn't always act together, especially not when performing covert missions. There are going to be times where social skills are needed and Mr. Right Now is going to have to pull it off because Mr. Right isn't in a position to do his thing.