don get me wrong. i too, use stainless steel fixings.. and its because they are likely to rust less, and be more likely to undue easily.
one only needs to see the reaction of the aluminium wheels with the steel wheel bolts to see the electro chemical reaction i talk about... the dreaded white powder ... aluminium oxide..
pretty much anything that comes into contact with water ( the activating agent ) will show similar reaction, and folks know that and deal with the results..
like.. seizing door window mechanisms, failing alternators... duff fuse connections,, bad earths,,, hood mechanism rust,,, and the growth of rust spots, and seized steel bolts, particularly those that go into aluminium.. or remain undisturbed
wherever possible i still use an insulator... to stop or reduce the reaction between dissimilar metals... like grease, or oil based lubricants, plastic insulators...
paint - etc... on any thing that doesnt rely on clean uninsulated contact - like electrical fixing points... those i just have to keep clean and maintain more regularly..
for those that like show cars.. dedicated time spent cleaning to make things shine.. isnt a problem.. bt my F sits oustside and is doing over 80 miles a day in all weathers... and until recently i was leaving home in the dark and getting home in the dark for the last 5 months plus.. 4 days a week.
so insulation is still my preference over metal to metal contact where possible.
and if one considered that the whole car body steel was so insulated by coating , before it was spray painted,,, and mine is still going strong, though beginning to show failure now.. after 17 years... then i think insulation wins where possible.