Because Spain is crap at ensuring proper taxes are paid?
I understand that Chopera but the actual fact a law is in place to provide a requirement for rental licences should be enough for the ‘investor’ to accept it could be well enforced either currently or in the future.
Incidentally Spain is actually getting much better at collecting taxes. Possibly through EU pressure to reduce debt and dire necessity. The government are now systematically trawling through local Empadron records, then sending round inspectors to the address to see if these records are accurate and if the property is rented out.
Central government pay local councils a fixed sum per year, per head of Empadron recorded residents. Tax bills due on rental income no doubt will follow. 🙁