I usually try to single point the threads in my lathe to about 85% and then just use the tap to clean up and bring the thread to the right size.
When I took my machining class a student asked this question. The teacher basically laughed. Single point thread, use a gage to ensure specs. If you are threading, single poit and use a gage or thread wires to ensure correct specs.
Oh, I've been known to do the same thing, I use the tap to clean up the threads.
If you are making a part that can use class 2 threads, then this is a possible shortcut. The tap will follow the almost complete thread path left by single pointing. It is a time saver because you can forget having to have a gage or the mating part, and sneaking up on the correct fit.
That being said, I wouldn't use a tap for suppressor use because of possible misalignment, however small it may be. And yes, it is a pain in the ass to single point small internal threads, such as 1/2-28. You can hardly see whats going on due to the tool taking up most of the bore. You also have to have the mating part or a gage to check as you go. But that's the breaks.