Sometimes people get set in their ways and don't want change. If you look at indoor rowing where Concept2 machines measure power you see most rowers and coaches ignore the watts and work entirely with pace. When you are working out training plans and looking at performance it's far easier and logical to look at the watts and work on percentages and ratios. A 5% increase in power does not give you a 5% increase in pace rowing etc etc. But because rowers communicate in stroke rate and time / speed most don't understand what a watt is so ignore them.
I suppose if you are a minimalist and want to minimise gadgets and keep your running very zen you would prefer not to measure your running power, but then if you follow that through you would dump the watch too.
I can see a lot of uses for them.
When I did a lot of running there was almost nowhere flat. I used several routes and my average pace was different on all of them so you couldn't compare a runs. Surfaces also affect pace. Even slight undulations affect pace. Then when you move and train on different routes you can't compare your training on the new routes with your old routes and years of training data becomes far less useful.
A question. When running do we see increases in speed requiring greater percentage increases in power, e.g., does a 10% increase in pace on the flat require a more than 10% increase in power?