I think a lot of times the schedulers don't know, or don't want to know, what is involved in a shop. For example, there is an Arches near me that was once the highest grossing Arches in the world (I think it is second now). I declined that shop time and again. I could not make the schedulers understand that not only will a bus be parked there, likely there will be 8-10 tour buses parked there. Unless it is a 6 a.m. breakfast shop, there will always be 8-10 tour buses parked there. That's why they are the second highest grossing Arches in the world. It's not possible to shop lunch or dinner there without tour buses, which in turn invalidates the shop.
Trendsource has some grocery shops that I would not do in a million years. Each of that chain's stores in my area has had at least one murder in its parking lot in the last year or so. The stores are gang infested. When you walk into any one of the stores, it smells like rotting, maggoty meat. Any food I bought from the deli or the meat case for the generous $8 allowance would go straight into the trash. Therefore, I refuse to risk my life and spend a minimum of 30-45 minutes in the store for almost a dozen interactions for the $5 fee. But the shops get done every month so someone is willing to do them!
There have been others that are in really dangerous parts of the big city or high crime areas. It is not greed nearly as much as it is safety sometimes.
I stopped doing MF's Arches shops because the route I was doing, which was heavily bonused ($320 for four shops) was very remote and I would camp overnight to get them done. I don't camp in the wilderness without my dogs. They stopped allowing the dogs to go through the drive thrus with me thus I stopped shopping them. I have no idea if the new person is getting the same bonuses, or even more. You can't touch a fleebag motel in the area for less than $100 a night and one that I would actually stay in is about $200 a night and they have to be done over a two-day period.
My point is that there are many reasons not to accept a shop and not all of them are economic.