Because CZ churns out more 'police' pistols as aftermarket. They are not really interested in doing market research to get to the public. They seem to want to sell what is in a sense 'surplus'. It is easier, and their guns still sell.
OTOH, they would BLOW away SIG and others with a lightweight, accurate and reliable, slim, and ergonomic compact pistol. Who would NOT want one with essentially a 1911 operating system? But, that would require a slight mod to production that they are not willing to do.
It's dumb - but it is easier.