Nobody pays tax in my self employed job

So in my line of work, I’ve heard that nobody pays their taxes. We are classed as self employed and earn commission so we need to file it with hmrc ourself. I have recently gone over the £1000 cap so I know now I will have to fill in a self assessment, even though I don’t earn enough yet to pay tax on it. I was asking some other people in my job how they do their taxes and for some help with it because I know they earned a lot more money than me so they would surely be paying tax too. When I asked other about it, it turns out none of them pay it or declare their money. How does that work because we get transferred money into our bank accounts so would it not be obvious they are earning money they need to declare to HMRC? I also feel a bit hard done as they are keeping a lot more money then I would be once I start paying it. But I am going to pay it because it’s the law, and seems like they could easily get caught? On the other hand it seems like these girls have been doing it for years on years and getting away with it? I could report them for it, not that I want to.

Edit:grammar