I agree. It's also incredibly difficult for those who haven't practiced as you have. The few times I have tried it (in safe conditions) I have ended up braking far too hard. My left foot somehow doesn't have the "feeling" of my right foot on the pedal.
One racing driver technique that can be useful in normal conditions (in a manual) is heel-and-toe braking. I use it to avoid excessive engine braking while downshifting, and sometimes for hill starts without using the handbrake.
It's much safer if that how you learned to drive from day one. Unfortunately most existing drivers don't have the skills to safely left-foot brake so that's how we teach new drivers.
You are right! Its not a common skill. Im left handed so left foot breaking feels natural to me. Plus I drove manual cars for years and am used to feel the clutch/brake bite with the left foot.
It doesn't take long to get smooth with a left foot.
Also left foot braking is much more useful day to day than heel-toe. Especially if you ever deal with suboptimal traction. Plus, faster reaction times.
Heel-toe is also dependant on the pedal placement and clutch weight. But I don't see it being useful in day to day. Rev matching is not something you do on daily driving. You usually tend to short shift at lower rpm.
One racing driver technique that can be useful in normal conditions (in a manual) is heel-and-toe braking. I use it to avoid excessive engine braking while downshifting, and sometimes for hill starts without using the handbrake.