I think the thing that gets in my craw mechanically is that as you point out, a non-standard wizard will always be behind from the start of a campaign to pretty much the end, which few campaigns reach anyway.
This says it all.
People want to min/max, not for the character role, but because they don't want to feel like they're behind. It's not the role playing so much as it's the roll playing.
In my personal experience, when people at an rpg table are mechanically punished for playing out an idea they like, they retreat and withdraw into themselves, but when you allow them to live out the fantasy they wanted and feel like their character is competent while doing so, they relax, open up and the real roleplaying flows out of them naturally.
Have you ever played a campaign feeling the whole time like you're behind? Can you truly say it didn't bother you? I'm not trying to trap you with this question, it's just that you say it's "roll playing rather than role playing" as if those two were entirely disconnected, when I believe they're not. Anything that increases your enjoyment of a character is ultimately good for roleplaying.
