This may also illustrate the why:
Today I was surfing, with my wing flagged out, on knee to waste high swell, for 1.5 mile long "waves" down the river. Then, instead of getting caught inside, dealing with any crowd, I just sail back upwind, and start another, 1.5 mile "wave" ride back down.
I racked up 40 miles of travel which potentially means 40% wave rides? So, I scored 16 miles of wave riding in 3.5 hours, or almost 90 minutes of actual on wave riding in my session. When is the last time any of us got 90 minutes of wave time in an entire year?
All that being said: Actually riding a SUP on a real wave is very different. It's magic. Just like riding a surfboard is. It's all different forms of magic and it simply comes down to what is available on any given day. When the surf is good, I still want to SUP surf waves. I just don't want to drive 2.5 hours to SUP surf when I can get 3.5 hours on foil 30-60 minutes from home.