Not trying to be argumentative but why does it have to be a level playing field? Why can't some races outperform in certain areas? For instance, let's use the orc wizard as an example. I assume people roll an orc wizard mainly to roleplay since the orc (I think) racial traits are not that useful to a wizard. People roleplay orcs because of the potential conflicts that may arise. If that's the core reason, why the need to min max our stats? An 18 vs 20 is a minor difference after a couple of ASIs but it seems like everyone needs that 20.
People tend to follow RAW if they can. That way if you happen to play in a different table, you don't have to concern yourself with a bunch of homebrew. It allows the game to be consistent. So yes, I agree, you don't need permission but it's better if the official rules were followed by all.
Because fundamentally being worse than the rest of your party doesn't feel good.
People may roll an orc wizard for a variety of reasons. Some might do it for the racials (Savage Attacks isn't useful, but a wizard can still get great mileage out of Restless Endurance in a pinch) while others might just really like the aesthetic of a burly half-orc in wizard robes. Others might just want the novelty or to roleplay a character who, while competent in the field (has 16 INT), isn't respected by their peers because of racial bias. Or heck, maybe they just LOVE half-orcs as a race and really want to try wizard out.
What Tasha's rule does is allow the player to not be penalized for choosing flavor over mechanical strength. Or at least not punished as harshly. Being 5% more likely to fail at casting spells as a wizard is generally not good. It is why you almost never see a human or gnome wizard who sets their INT at 14 and feels this is fine. You always want your character's primary stat as high as it can be so you can succeed your important rolls as much as possible.
There's also the point that some campaigns are harder than others and some groups emphasize min-maxing more than most. In BG3 terms there are different difficulty settings, and maybe I want to play a half-orc wizard on a higher difficulty without turning it into an exercise in masochism.
Meanwhile if I DID want to be masochistic... I can always just not invest in my INT attribute when assigning my attribute points.
As I've said a few times now, all Tasha's rule does is add more options to character creation so that we can all make the sort of character we want without handicapping ourselves in the process.
