If it was a scam none would ever fail, and they do. I've had two fail and be taken away by the police for investigation, one was destroyed I believe as it was a ringer,

If the test only takes 5 mins, then it means it was a legit car and the Id matched and didn't need any time investigating there is still a process to be completed,
There is also a fair bit of paperwork to do behind the scenes as well as removing the vic marker etc etc.

They are not all like that some take quite a while, especially cat a and bs,

It's a little narrow minded saying its a scam as yours was easy,
it's just like saying the mot is a scam because your car passed in 25 minutes. That doesn't mean the next test through the door won't take an hour and be a shitter though

Try taking a ringer in for a vic, you may be there quite a while and be escorted away by the police. Would that justify the cost to you?