There is no way to know who shops where without signing up. It’s not like you are just throwing your personal data around…you are signing up with legitimate companies for contract work. Looking at who shops where on a random day doesn’t tell you a thing,,,ask the shops may be gone for the month or they all may be dropping the next day.
One of my best shops was for a company I had been signed up for over ten years without a peep. And then one day they needed someone for a very easy $150.00 shop. It required a partner and I took my college age daughter, The shop required a purchase, two pictures and returning it in as found sitting on a bench, It paid in two days. Well worth being signed up for them all those years,