That's definitely a problem too, but I don't think that's the whole reason. I think this is an extrapolation of contracts which are a good thing where appropriate. An agreement between parties, ideally with input from both that everyone understands and agrees to.

Now, we make dozens of 10k word (or 100k word) agreements every week that no one understands. It would cost thousands or tens of thousands to understand them. You can't read them all and even if you did, you would find that being the odd one out in this regard left you unable to get a hotel room, phone or read a newspaper. So, we lean on standards, norms, consumer protection laws and to keep us safe from these damned contracts.

Common law (or my lay understanding of it) suggests that there is grounds for completely invalidating a "contract" which no one expects any one to read. If either party don't know what they're agreeing to, it's not a contract.

I'f you hand me a one page, large font bullet pointed list of things to agree to, that is something you expect me to read. If you hand me a 40 page small print book while I'm standing at a counter with people behind me, it's obvious what is going on.