I hate the no headphones rule and is incredibly harsh if people are disqualified, might be in the rules, but running should try and be inclusive as possible. I can always hear marshals and cars with my music on, if I go the wrong way or get run over then it's my loss.
Deaf people are allowed to run, what's the difference?
I've been warned by lots of marshalls at the end of races that I could be disqualified, it hasn't happened yet though. If races start enforcing it regularly and I therefore don't get a time etc. I'll stop entering races and just happen to be running the same route at the same time.