You can get a cathodic reaction anywhere steel and aluminum meet; there is not a whole lot you can do about that, other than use a non-magnetic stainless w/ alum, or if it is between a fastener and aluminum a coating of synthetic di-electric grease like "super lube" helps to break the bond between the two metals.
the only thing i can think of is that those who do, have a different management hierarchy between the frame design department and the "brazon-on" "doodad" department. more likely, they just don't care. IDK...
those are riv nuts .. scrape the paint down to bare metal and do a little touch up paint job.
What others have said, and while it is cosmetic and you dont like it, dont worry. Aluminium frames are quite thick and you are in no danger of having a failure.
I use Boeshield T-9 to treat areas you speak of. Prevents corrosion on various parts of the bike and it's an excellent long lasting chain lube.
Mythical Creatures Touched Me in my Bathing Suit Area.