While I don’t think 17x8.5 +00 and 17x9 -12 are the best or most functional fitments they are the most abundant. 17x8.5 +00 and 17x9 -12 are the most common fitments wheel companies build so by default they’re the most sold. Biggest reason behind that is the ability to fit a multitude of vehicles without paying for multiple molds. Cast molds can be 8-10k per style/size so it doesn’t make financial sense to have multiple molds for multiple trucks.
GM trucks can take lower offsets without the wheels poking out much. It’s been this way since the 2014 GM 1500’s came out.
Toyota Tacoma & 4Runner require 4.75” backspace to run oversize tires without hitting the UCA’s
Lifted Jeeps also require lower offset for proper clearance.
Even though these vehicles use different bolt patterns and center bores the same 17x8.5 +00 mold can be used for F150/Raptor. They just drill the pattern and change the center bore.
That aside, some people just prefer a wider stance