I really learned more about the game as a player than as the DM.
When I had to figure out what I could and couldn't do within the framework of the rules, and how to set about doing that.
I like dice. I hate diceless systems. I consider them an aberration.
But...there are times when I'd just like to succeed instead of maybe kinda sorta succeeding if the dice let me.
There are times when it doesn't matter. Appraise checks, for example, strike me as being an insane thing to min/max on.

But Pick Pockets or Sleight of Hand isn't something you want to mess up on.
Especially when failure means incarceration or worse. So I will usually min./max my rogue so that when I say, "I pick his pocket" I mean that "unless I roll a 1 or he rolls a 20 on an opposed check, I pick his damn pocket."

Failing a saving throw, when it means you might turn to stone or worse, also holds no allure. When I'm not playing a rogue or other skill based PC, then I usually min-max on saving throws. I thought of a Dwarf Rogue who was nearly immune to poison in case he blows a remove traps roll, or a Dwarf Ranger with favored enemy of Wyverns who was nearly immune to their poison from having suffered so many stings over his career were good hooks.