It amazes me how aggressive people can get regarding topics they have zero knowledge about. You are not entitled to your opinion. You are entitled to your informed opinion.
So why don't you see to know about national agreements in regards to the different categories of actor who might be on a set?
As for having a film degree - big deal, you have a undergraduate degree it means you know not very much about a range of subjects, it doesn't make you an expert in any sense. If we wanted to play that game, I'd just turn to my right and ask the wife - who actually *is* an expert in this area.
It has everything to do with their contract!? That's how the industry like.... works?
Wow... go away and do some reading about how contracts work in the TV industry for background and day players (especially in the US which is what we are discussing), then come back and you'll be able to construct this fantasy a little more convincingly.
I'm not cruel however, I'll give you some terms to search for "Walk-on 1, walk-on 2" which are specific to the UK industry.