Why can a sign that someone may or may not have read be considered a binding contract?

Just curious, but those car parks that have the signs up say that the sign is a binding contract, is it really that simple?

If I put up a sign in big writing and say it forms a binding contract, I bet I wouldn't do well if somebody challenged me in court.

So how come they can go "well we put up a sign and that's it mate. Legally binding contract, no backsies"

I mean the law can't even require you to be literate, or have English as your first language, or be tall enough to read the sign (they're always up high) or be legally trained enough to know what a contract is let alone the one on the sign and decide whether you would be happy to agree to had you understood it. So how can they justify the equation "Sign put up = legally perfect binding contract"? 

I should point out I have not been sent a charge or anything, I really am just curious.

Alasdair Taylor's answer to Why can a sign that someone may or may not have read be considered a binding contract? (1557797852)

Perhaps it would have been better if the private parking penalty system in the UK was not based on the law of contract. It doesn't fit particularly well with some of the core doctrines (offer / acceptance, intention to create legal relations, certainty, etc).

For some background on the legal and practical issues, see this article form Quality Solicitors:

https://www.qualitysolicitors.com/small-claims-service/parking-ticket