I've never seen anyone mention this, so here goes.  My son got into car painting for awhile.  He repainted the door on the Fiero.  He tried several times but just couldn't get the base color to look at all smooth. We talked about a clear top coat over acrylic enamel and he eventually said what the heck.  So he put on one coat of polyurethane clear top coat.  The next day it looked fabulous- smooth, glossy, almost perfect.  But if you looked closely you could see that all the imperfections in the base coat had nearly disappeared under the top coat.  They obviously still had to be there but they'd turned nearly invisible.

A while later we were looking at cars and happened to look at the Corvette on display(not seriously).  I noticed the hood and rear deck looked absolutely gorgeous- totally smooth, no blemishes or anything to be seen.  Then I looked at the doors.  They looked just as good at an arms length, but if you got up close it was obvious that the yellow paint underneath was pretty prominently orange peeled.  But from a couple feet away the clear coat made it disappear.

We also saw something similar on an ARF plane.  One of the guys in the club had a Brodak Oriental ARF painted with very light clear top coat.  All the covering edges bumps, etc. disappeared.  The extra paint only added an ounce an a half or so.

So I guess that's why 15 coats of clear dope, sanding and buffing out, and polishing aren't really required.  The polyurethane clear does all that with one light coat, plus its a lot more fuel resistant.  From a distance its hard to tell, but up close the dope finish looks a little softer or 'deeper'.  Either one is way better than the crappy finishes I prefer.