Can we live without it? Depends...

I don't understand why RC in USA is addicted to Nitro. As a result, engine manufacturers have designed their engines to take this into account. Maybe they got an agreement with the fuel makers who knows.

Now, why do I use 15-20% nitro in my engines? Because the engines I buy are low compression engines and need it.

If you buy a high compression engine you can get away with using little, if any. Unfortunately, you won't be able to buy OS and other popular brands.

Many of the European engines are high compression and are designed to run on FAI fuel. If you put nitro in them, you'd suffer from detonation. You can add head shims to a high compression motor to reduce the compression ratio and than you can use the nitro and possibly develop more power. To do the opposite to a low compression engine such as an OS .46 would take some more work such as milling head and/or messing with the squish band.

Nitro has its advantages though but I think we Americans have fallen prey to marketing..