It can be considered impolite or insensitive to ask someone if they hire a cleaning service when you're a guest in their super clean house. While you might be curious about how they maintain such cleanliness, it's important to remember that personal cleaning habits and choices can be sensitive topics for some individuals.
Instead of asking directly about hiring a cleaning service, you could express admiration for the cleanliness of their home and compliment their efforts in maintaining it. If they choose to share information about hiring a cleaning service, they can do so willingly. However, it's best to let them initiate that conversation if they feel comfortable discussing it.
Respecting others' privacy and personal choices is key when engaging in conversations about someone else's home and cleaning practices.