Binbogami was trying to stop Aya's family from duping other people with their business. Even after Aya was born, why on Earth was he still staying at their house since they have fully broke.
Its a good thing Zashiki-Waraki gave their family some short-term fortunes but they misused by taking granted of him!
Anyway, Aya-chan so cute!!😍💞

I guess I understand why Binbogami didn't fully trust Aya's parents. He probably sensed they changed, but wasn't sure if they would be good people if he left and a dubious opportunity came knocking.