Yeah. You may eventually wind up with a well-seasoned pan.
I don’t know for sure. I do know that somebody once used my steel bread pans (which are ordinarily never washed) for something else, we had to scrub them to get off that something else, and it took years to get them back to where the bread didn’t stick.
I use a toaster oven for almost everything that needs to be “baked” since I don’t see the point of heating up my full oven fpr small things. It came with two pans, one solid and one with vent holes. I mostly use the latter, with a sheet of aluminum foil to keep from having to wash it. Over the years they’ve both managed to get stained and I keep wondering how I can clean them. Thanks to this thread I have decided not to worry about them any more. Someday when I’m feeling ambitious I may get my container of Bar Keepers Friend and try to clean them. Right after I go through my book collection and box up all the ones I don’t want 
Good to see your priorities are correct.
That’s the way I prefer them. My doesn’t cook much, bakes occasionally, she likes to see a shiny like new baking sheet. I like a pan that improves with age.
Personally, I would not worry too much about stained baking pans. As long as they are not changing the taste of the food or making unpleasant smells it just means they are well used (which, to me, gives me some confidence the cook actually cooks). Pristine pans are not a requirement. I suppose they may matter if someone wants an immaculate look in their kitchen but that likely means buying a new pot/pan on a regular basis.
There are limits though, like in the pic earlier in this thread. A little grunge is to be expected but a lot…not so sure.
I will second this. Bar Keeper’s Friend is weirdly good at cleaning tough pans. I have found nothing better. Not sure it should be used on non-stick though since it is abrasive.
But where were you in the 1960’s when TV dinners were served in most American homes?
Or was it your mother doing the prep of them?
This is my entire approach to my kitchen accoutrements.
I have NO nonstick pans; everything is either cast iron, steel (my hand-hammered wok), or un-clad aluminum. Even my loaf pans are cast iron…
I’m not @glee, but I’m pretty sure the answer is “growing up in the UK.”
Yup, growing up in the UK. 
Aside from some of the excellent advice offered here about cleaning the baking tray (not that I think it matters for hygienic reasons – it’s purely aesthetics) I second the advice about parchment paper. It’s a marvel that prevents food from sticking or ever touching the baking sheet. It also means that you usually don’t even have to bother washing the baking sheet/tray – just throw out the parchment. If something is going to be exceptionally greasy/messy, I might line the baking sheet with aluminum foil, then put parchment on top of that for its non-stick quality. Sometimes I even use parchment paper in the air fryer. I find it so useful that I buy it in extra-large bulk rolls.