I guess the biggest issue is you would need time up your sleeve

To grab a board, drive some were and jump in takes time as it is, but then add hook up boat trailer, launch at a spot near were you want to surf, travel to that spot and then anchor up, Retrieve anchor, drive back to ramp, retrieve boat and drive home, wash boat and trailer i can personally can see a at least doubling of your time

Not to mention yearly registration, service costs and boat license.
BUT I guess if you live close to a spot that requires a boat than you may get the value, obviously many do and then i guess you've also got a nice setup to do a small spot of fishing or other boatie type stuff

The funny part for me is although i've dived for years, i just never feel that comfortable/confident anchoring near surf breaks and leaving the boat on its own. I guess that could be because i often hear horror stories from others who have had issues