As Brazilian Jijitsu folk like to say?
BJJ came into its own on the beaches of Rio. In that environment, on the sand, it's hard to stay on your feet in a fight. Where I live, NYC, it's all concrete. Even though I'm a more technical grappler than 99% of the population, the last thing I'd want to do is go to the ground.
Also, in today's MMA environment, the day of the one dimensional fighter is over. The fights get stood up too often. Combine that with the 3-5 minute rounds, and a pure ground fighter has a good chance of getting KTFO, as evidenced by the Dan Simmler fight and several others.