Interesting question! I have used a stepper motor controlled rotary spark gap before so to have very precise control over the timing. That of course also requires some other modifications in the HV source, but this precise control was at that point my main focus. The result was that I could generate short pulses at a rate up to about 30 Hz, using up to 3000 Watt.
Now, I would like to operate in a more continuous mode and with more power. 30 BPS is way too low to accomplish this. Also the voltage in the primary circuit is up to 44KV (from 11-22KV earlier) Now it is difficult (but possible) to design a high speed spark gap for 44KV, yet to do it right you will need to adjust the timing of the spark gap to the frequency of your source (50 Hz) and that makes it very complicated.
-- here is an excellent source for more info on that subject --
A static spark gap is by far the easiest solution in this case. And the multiple gap design makes the extinguishing easier.