It's about increasing the compression ratio without self-ignition. High compression ratios mean higher power for the same weight, and airplanes are all about m

It's about increasing the compression ratio without self-ignition. High compression ratios mean higher power for the same weight, and airplanes are all about minimizing weight. You also get higher efficiency. Again, lower fuel weight = good. You can dump as much fuel in the cylinder as you want (in fact, most airplane operating handbooks call for a very rich mixture on takeoff because of the cooling effect).