Your Airbnb host is most likely the owner of the rental or hired by the owner with salaried or commission-based pay.
If you think of it like that, you would not tip the owner of a restaurant as they are receiving all profits from your business.
Alternatively, you would tip the waiter, as they are directly providing you with the hospitality and service that determines your enjoyment and experience.
Like the waiter, you are welcome to tip the housekeeping team who cleans the Airbnb rental or any additional workers who improve the quality of your stay. Many Airbnb’s in my area provide envelopes just for the purpose of tipping housekeeping for a job well-done.