Although it’s not necessarily the agencies fault, you would probably end up working in some places where you’re treated like crap.
You would have hours of shifts on your feet and you’re not allowed to sit down for a second or even lean on something, they don’t care if your feet hurt or anything.
You are sometimes given a uniform which could be a flimsy shirt and I you could be asked to remove any thermal wear or undershirt, so you could be freezing during winter but guess what they don’t care.