Poor people might not have good options, because they have no money, but they have options. If the check cashing place on your block charges too much, you can go to the one down the street. The barrier to entry in these markets is so low that there is no argument that they are "gouging" customers who have no other options.
Focusing your ire on check cashing places is the archetypal example of a bullshit solution crafted based on emotions rather than rational analysis. Forcing check-cashing fees below the market price is just going to reduce the number of check cashing places, taking away options from people who need them. Any real solution is going to either require the government writing a check e.g. by subsidizing bank accounts for poor people, or reducing regulation to lower the transaction costs in check depositing and withdrawals.
These are businesses that survive by making lots of irresponsible loans to people who have no business taking out loans, funding them out of the enormous fees and interest payments charged to the subset of their customers who aren't total write-offs.