The credit check is not to do with the franchise fee but the group fees. If you did require finance, from say a bank, the bank would also credit check you. The reason SW do a check is, as a Consultant you will be responsible for all the money from the group session, so they deem it necessary to check that your credit file is good. SW will take their money out of your nominated bank account on a weekly basis.
It may also be because, as well as group takings they are intrusting you with stock and equipment.
Hope that makes sense, good luck x