@Imanol9 Airbnb determines the percentage of guest service fee. Hosts have no input into this, nor are we privy to how their pricing algorithm works.
There are 2 fee structures available to hosts. One where the guest is charged aa service fee of, on average, 14.5%, and the host is charged 3% (called split fee) and one where the host pays all the service fees (called simplified)
The one where the host pays all is really just a marketing gimmick- the guest doesn't see any service fees tacked onto their bill, but their total end price is the same, as hosts have to raise their nightly price to cover the added fees they are paying.
Example:
Split fee- Rental is $100/night. Guest service fee is $15. Guest pays $115 total. (Host makes $100 minus the 3% host service fee charge)
Simplified- Rental is $115/night. Service fee to guest is $0. Guest pays $115 total. (Host makes $100 after deducting the $15 service fee they paid )