The problem is, we have an extremely litigious society, and lawyers are asked to think through and address all of the risks. The lower the dollar amount, the lower the liability that a company can reasonably take for the transaction.
Do you want to have an account? Great, but we need to be clear about who is responsible for use of the account and its credentials. We also need to clarify when it can be suspended or terminated. Do you want to submit content? Cool, but we should confirm that what you submit is your own responsibility, and we need to add some language about ownership and licensing to avoid copyright and other IP issues. We should also confirm that certain types of activities are not OK (e.g., pornography, harassment). Do you want to provide feedback? Awesome, but you cannot sue if it is used. Do you want to use APIs? Sweet, but there are things you can and cannot do so you don't break or abuse our system. Are you paying for things? We need to be clear how that works. And through it all, we need to have key provisions about warranties and limitations of liability so the business is not on the hook for millions when the account is worth $10.
And all this is for a simple service. There are countless ways to add complexity to a service.
I still agree with a ton of points here about the dangers of one-sided agreements, limited options for services, complex legalese, etc. But I will say that this is a trickier issue than people seem to give it credit. It may be nonsensical to say that a consumer read and understood a contract, but it is also nonsensical to say that companies should risk bankruptcy for free or cheap services (unless we are OK with free or cheap services no longer existing).