Do pilots typically carry oxygen at these events?

If you're going to fly xc at any site that allows you to get over
10,000', oxygen is a must. Forget about speed, as a beginner you're
going to want to be at the top of the thermals because you don't want
to think about landing out. Planning to bail out of thermals below the
top for 02 reasons sets you up for a needless mountain of stress. The
mountain high system is great, and the small ones are easy to install.
Yeah the FAA says you can go higher, but you want to make good
decisions in stressful situations. I set mine to go on at 5000' after
seeing at Tonopah that my o2 saturation was 95 % and heartbeat 10
beats above normal while sitting on the runway.

John Cochrane BB