Trying to be emotionally engaging while punching in two words on one vocal line is no fun - either as a performer, or when trying to capture someone else's performance. What makes a good vocal performance, however, is when the performer is really into it, and the engineering doesn't intrude at all. By not doing punches, a vocalist can come in, do some quick, loose takes, then kick back. Comping may sound like it's designed for when you don't really know what you're doing and want to fix it in the mix, but that's not the idea. The intention is to capture spontaneous moments, and then perfect the performance offline.
Some singers go downhill the more they do, whereas others get a second wind.
It's different for each individual. In Fig. 1, note the gap in track 001. After the first part of track 001 plays, the next highest-track is 003. After its segment plays, the segment in track 004 plays. Then track 1 is once more the top-most track, and it plays the remainder of the solo.