In practice, most people find the heuristics themselves much more useful than the process of applying the heuristics. This is probably because exhaustively analyzing an interface is literally exhausting. Instead, most practitioners learn these heuristics and then apply them as they design ensuring that they don’t violate the heuristics as they make design choices. This incremental approach requires much less vigilance.
I can see how this would make a lot of sense because trying to review every little detail of a design is just tiring. I also believe that it's just easier to simply have the heuristics at the back of your head as you design as opposed to having to go back and look over everything later. It's almost like being cognizant of good habits beforehand so that you don't need to make adjustments afterwards. But simultaneously, I do think that if you rely solely on heuristics, you will miss some of the problems that real users would spot. So although the approach is helpful, I do think that testing out the design with users is equally important.