First - because the folding tri is the best possible sailing boat between 22 and 36 feet, combining speed, trailerability, reasonable internal space and simplicity.
Second - Almost no competition. Ian Farrier invented the folding system and patented the idea. The patent expired recently and the first serious competitors are just starting to appear.
If you have time, also check the Catri 27 - the folding tri I decided for, after a similar research.
Cheers,
Luiz Schechter
Catri 27 R