Ok, let me break the argument down for you:
1. Person needs job
2. Person doesn't have job
3. Person therefore is low on money
4. Person needs to prove right to work to get job
5. Person needs money to buy proof of right to work (+ time to receive it)
6. Person needs money
7. See 2 and 3
Your privilege is what blinds you to a simple process.
> If you are looking for work you really should make sure you have these documents as you should know that you are going to need them.
This is what I mean by "your privilege is showing."
> That to avoid fines an employer would break the law and not do right to work checks? Or that they are doing a right to work check and do additional checks?
Read it again: they're skipping the checks and just using the one they know (passport) because they don't know if other legal forms of documentation are good enough. I know this is going to blow your mind but plenty of employers have no idea what the laws are. You might say "well that's on the employer," but it's the person who needs the job who suffers.