It's extremely difficult to represent yourself pro se if you don't have access to information about how cases like yours might unfold, arguments that have been used, how well those arguments have worked, how the cases have been decided, whether a company has settled a similar case as yours, and so on.
It's just too important to risk no?
Like DIY surgery. It's quite expensive and impenetrable to be doing your own appendectomy and I'm not mad about that. In both cases you could if you really had to but a high barrier to entry for me is not a bug but a feature.
Not in US you don't. Leaving aside how you don't have a right to a lawyer when you are on either side of a civil matter, most states will send you a bill should you avail yourself of the "a lawyer will be provided for you" part of the Miranda rights. Now, if you are broke, they'll still provide services to you.
In Canada you actually get free legal advice before any questioning.
If you're in prison you also have nearly no rights to a lawyer. (For example, if you want to sue the prison system for inhumane conditions)
Edit: For ex you may need to pay fees to be allowed to drive, which you may need to go to work/buy food.
You can't get a windfall as a criminal defendant, just a conviction or not.