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.
I don't know that is the only reason. I can see that as a reason but defiantly not the only reason. For one I Have Asperger syndrome, its basically high functioning autism. I don't min/max because i want the limelight at all, that has never been a reason. I just like making effective, efficient specialized characters. To me character generation is one of my top three things in Dnd , more then the role playing aspect that a lot of you like. I am not really big on diplomacy, to me sometimes its a means to an end, but i never rely on it. I prefer combat, if you look back to the start of dnd it was meant as a game of strategic combat, not diplomacy. Diplomacy maybe how you start encounters, but it still a secondary thing compared to combat in DnD as a whole. Third my last favorite thing in dnd is really just watching the character i mapped out before it ever got put in a game reach its potential.
I generally start thinking of a character starting at lvl 20 and work backwards to lvl 1, and how it work back up to lvl 20( or whatever the lvl cap is for the game i am playing .) Asking what lvl the game will end at is always my first question to the DM. Because i can't even start a character til I know that. I start with class, then race, then i focus on ability scores. But the whole idea is to just focus on a single aspect. That may make them great in a specific situation, but I will say it again... there is a saying "too much specialization breeds in weakness." And trust me , if you multiclassing there will be some lvls your behind , normally in areas like ASIs, but sometimes you can catch up.
It takes me on average in a dice and paper table top game an average of a week to make 1 character, because so much thought goes into it, that and i write out every skill ,feature, spell or ability they get from lvl 1 to 20 on the sheet as notes. I even go through and do spell list from lvl 1 to 20. I plan it out 1 character lvl at a time, that includes spells i am adding and spells i am replacing. Then just notate when the spell , ability feature so on became active or inactive, thats what i meant by "mapping a character out." I have played Dnd since 1st edition when i was like 8 years old. For me I know what combinations are or are not effective. I might make adjustments to my mapped out character as I go along , but most of the time it stays as written. when i write a backstory, my backstory has a backstory. This allows me to go past my story to even deeper into character. writing the backstory for me is the easy part.
While i do min/max, i like it there are people that are more into diplomacy or mental puzzles. A character shouldn't be good at everything, but should excel at what there focus is. Also a party shouldn't all be good at the same things, everyone should have their own specializations, the thing that gives them value in the party, because the game is meant to be a team effort. Also because that means i don't have to do the parts i hate, I let them do it. But when it comes to combat, thats what all my characters are built for.
