Oil volume should be in direct proportion to load, time under load and rpm. For example trials riders can run their engines at 80:1 because they spend a lot of time at very low loads and low rpm. When they run higher loads and rpm rpm it's usually just for short bursts, so the 80:1 is adequate. Motocross riders and trails riders tend to run higher rpm, higher loads and longer time under load. So more oil is required.
Most OEMs recommend 32:1 for a good reason, more oil is usually better than less. If you take the time to learn to jet, which is something only a tiny percentage of riders ever do, you can run as much as 16:1 in an MX bike without spooge running from the pipe or fouling plugs. I ran my MX bikes at 16:1 - 24:1 based on the course. I run my Montesa trials bike at 40 - 50:1 without issues. More oil tends to make better power and tends to make parts last longer, IF you take the time to jet the bike properly.
Most guys are lazy and rather than bother with tuning, they keep putting less and less oil in trying to keep the plugs clean.
Don't be one of those guys.