Surfed and windsurfed a lot in my teens and early 20s all around Devon, Cornwall and S Wales.
As everyone has said, you spend a lot of time not surfing/sailing, spend daft amounts of cash on petrol and vehicles. (if you hang around the beach and load wet boards on your roof whatever you are driving will dissolve!) To improve you need a lot of water time on a regular basis and the comparison with snowboarding is unrealistic - you fall over on a snowboard anbd you can just get up, the hill is still there and you can start sliding immediately, in the sea if you fall then the wave has gone and you are padding out back again - it is tiring when you are learning.
I swapped to SUP when I moved up country from Cornwall, they are great if you DON'T take them in the line up and steal all the waves - they can and this will really piss people off, they are also the size of an oil tanker when compared to a shortboard so need skill to handle in the bigger waves. Because they will pick up almost any swell you are able to head off and catch waves that the rest can't when starting prone so why fight for their waves?
But the best bit is you get maximum water time whatever the weather. If it's millpond then you can go explore the coast, anchored boats, etc if it's windy mine has two mast positions so I can stick a 6m rig on it and sail. And, if it's working and there's a good swell, I go fetch my Stewart.