Also, length of relationship is judged on how renewable it is not how long it lasted. You can fire anyone on their first day.

It’s really a question of how open ended the work is not how long someone spends doing it. A restaurant always needs people to cook food and a league always needs a referee as an inherent part of it’s business model. On the other hand a company might only need an architect when designing their new office, aka it’s inherently a finite business need. That architect can largely work at a location and time of their choosing, the referee needs to be where and when the games are taking place. Similarly, an Uber driver needs to be picking someone up at a specific location and specific time going somewhere else or waiting 1 hour doesn’t work.