Driver personality should be a distant 3rd on the list of reasons to watch racing. No amount of advertising is going to change how fans truly relate to a particular driver anyway. Should Joey Logano and Denny Hamlin's sponsors force them to make more public appearances? Probably, but at the end of the day their efforts probably wouldn't amount to much at least in the short to mid-term as far as benefit to the sport in general.
Only the most popular drivers make a difference here, and you can count them on one hand now.