[Mashiro]

It simply protects from automated brute force attacks which today are mostly 99% of all attacks thanks to huge automated botnets. 1% are the people you mentioned that would simply run a port scan or similar to find the new port.

That's usually how changing a default port to a non default port helps with brute force attacks. Generally this is helpful because it really stops all automated brute force attacks and thus can even drop down the load on the system (depending on the volume of the brute force attack).