On paper many states in the US actually have pretty strong protections for tenants for their security deposits. It's not uncommon for states to have fairly strict standards as to the valid reasons a landlord can take money out of a security deposit. If a landlord withholds money for frivolous reasons the tenant can be entitled to double or treble damages. (So if they withhold $1000 for no reason, you can get back that $1000 and an additional $2000 or $3000.)
The main issue is enforcement. If your landlord withholds the deposit, often your only recourse is to sue them (usually in small claims court). This is going to require paying some court fees, maybe on the order of $100 (which you may get back if you win, but you still need to pay them up front). Plus you're going to have to show up in court, which likely means missing work. And obviously you're not going to have a lawyer for this, whereas most landlords will.
When I moved out of my last apartment my landlord withheld $100 because he claimed there was dust on the blinds. (There was not, we specifically dusted the blinds before moving out.) But the only way I could get that money back was to sue them, and it just wasn't worth it for me.
I don't know about most states, but in Maryland, the tenent is automatically entitled to attorney's fees when the landlord improperly withholds a deposit.
Granted, if you are poor, this likely means that you need to find a lawyer willing to work on contingency.
For what it is worth, just threatening to sue along with citing the relevent law and possible damages is probably enough. Landlords don't like going to court either, so if you make even a halfway credible threat they will probably pay.
The main issue is enforcement. If your landlord withholds the deposit, often your only recourse is to sue them (usually in small claims court). This is going to require paying some court fees, maybe on the order of $100 (which you may get back if you win, but you still need to pay them up front). Plus you're going to have to show up in court, which likely means missing work. And obviously you're not going to have a lawyer for this, whereas most landlords will.
When I moved out of my last apartment my landlord withheld $100 because he claimed there was dust on the blinds. (There was not, we specifically dusted the blinds before moving out.) But the only way I could get that money back was to sue them, and it just wasn't worth it for me.