Maybe it's not that they won't do it but that they don't have to.
Of the HOT sisters, Arieth, Elena, and Heather don't do it, but maybe their tuition is already paid for because I don't think it's a pre-requisite that all HOTs have to not have it paid for. Riona, Sarah, and Melanie maybe do need help with paying which is why they're part of Quinn's business.
Of the HOT daughters, Camila has joined up and Mona likely will too. Lily seems like someone who would as well, Ashley's uncertain about it because she needs tuition money, and neither Maya or Josy know about it yet.
So joining Quinn's business could be conditional on tuition status; those whose tuition is paid for don't have to do it if they don't want to, but those who want their tuition paid for by the HOTs must join up or be kicked out.