3. Why would I spend coins on incubators?
Because you can't raid Azurill, Wynaut, Bagon, Beldum, Trapinch, Chimecho, Ralts or Slakoth. Hatching is still the most effective (or the only) way to get the hardest dex entries in many cases.
But I do agree that other than that eggs are fairly weak and could use something extra. Raising the IV range or the hatchable level could both work.