It is very common that heart valves leak a little.
Leakage is often classified as none, trace, mild, moderate and severe.
As long as the leakage is not more than mild, there is normally nothing to worry about.
In your situation, probably no further monitoring is needed.
Yes, someday you are going to die, but probably not from heart valve problems.
Agree with Ger57.
Tried to find some statistics, but was unsuccessful. However I'm pretty confident we can safely say the majority of the worlds population actually has some degree of tricuspid and/or pulmonic regurg. It's a normal finding.
In terms of how it happens, most of the time, you're just born with it. Anyone with the expectation that a few flaps of biologic material is going to create a perfectly watertight seal is kidding themselves.
Even if the regurg lacks the velocity to be identified on Doppler/ echo I'd still wager its there to some degree.