Thor I think its because IGA is not a charity or an org that helps people in need, and is an actual work place. if you want to do deliveries for orgs that help people then you would not need to get paid is my understanding
Paypal is very hostile to SPs, since they can shut down the account if they think they are doing sex work. Also, with Paypal, people can easely cancel payments, making it a very poor choice of platform to use to pay SPs