What is the definition of an incident?
In the aviation world, the NTSB in 49 CFR 830.2 defines an incident as an occurrence other than an accident, associated with the operation of an aircraft, which affects or could affect the safety of operations. That is fairly broad brush and could certainly encompass hundreds of possibilities. The key, though, is something that affects or could affect safety. 

A recent caller noted that five years ago he dragged the tail tiedown ring on the runway briefly upon landing and shaved off some metal. His question was asked in good faith, but one would be hard pressed to say that affected safety so, no incident. I am sure you can think of others from your own flying career that don't meet the definition of an incident.

NTSB requires an immediate notification of an aircraft accident or of an overdue aircraft believed to have been involved in an accident, as well as a dozen specific serious incidents. The hundreds of possible other incidents need not be reported. Whether or not they get reported, well, that's another topic for another day.