Funny Rod, they are the same reasons I lost interest in surfing after nearly 40 years being a fanatic. Always rode shortboards, did whitewater slalom canoeing with a single paddle for 12 years, then competitive goatboating for 18 years but always surfed.
Got sick of the skis, but must admit, I loved the ability to catch lots of waves (in the nicest possible way of course

).
SUP is the best of everything. I love C1 paddling, love standup surfing, love being able to compete with Mals and it's new and exciting. Have completely got my surf stoke back after 4 years Mtn Biking and hardly surfing!
I figured out one of the reasons it is so addictive apart from all the above. On my shortish SUP (9'3 ripper) it feels like you are riding an indo gun - lots of drive and speed - even when it is 2 foot!!