Most cyclists don't race, so the UCI regs are irrelevant to them. Even some races (notably triathlons) have much more relaxed regs.

That said racers do tend to buy a decent share of the higher-end gear, and the rest of people aren't sufficiently interested in performance to do the dorky things that will improve aerodynamics, such as using a fairing.

Aerodynamics is also highly counter-intuitive, which is why testing for it requires very expensive facilities and engineers.

And really, unless you are in an extremely competitive situation, it's mostly snake oil, as you're talking about (at best) advantages like "30 seconds over a 20km TT." Joe Average can barely quantify the differences produced by a $5000 aero road bike over a $1500 road bike in an accurate fashion.

Between the expense, narrow market and narrower advantages, there isn't much motivation to develop esoteric aerodynamic designs.