Elizabeth Warren (IIRC) had a talk about this.

The gist is that the common law principle that makes contracts enforceable in the first place is that they are understood by and modifiable by both parties. Somewhere along the line, that got supplanted by "sign if you understand and agree to these terms." Which, if common law were followed would be meaningless. Anyone can sign something, doesn't mean that that signature means that they understand.

But the courts have long since abandoned this principle. And so it has come as no surprise that contracts aren't comprehensible to a layman and as such, a layman cannot make modifications to it. Because all that is considered now is "did you sign?"

And so wise fools say now "you shouldn't have signed if you didn't understand the contract."

But with, say, a rental contract, the choice is sign on the dotted line or be homeless. The average person cannot understand what they are signing. Almost no one wants to go without shelter. So of course they sign. I need a car to get to work. So lemme sign that car loan.

Contract law was made simpler because you no longer have to prove competence out of either party. You signed.