...because the overhead of even small claims is bigger than what you can possibly recover in most regular disputes. There needs to be something like a class action for small claims - government regulators where you can submit complaints with evidence to and if enough people complain about a company the government has to look into it.
Isn't small claims designed for, well, small claims and therefore low overhead? That's why you can't bring a lawyer. Which is super annoying for a company, because a company has no physical embodiment and has to send a lawyer or other representative just by virtue of being a company.