Lots of money to be had in the litigation and problems caused. Same reason why gay marriage was pushed by these types. They don't give a shit about gay marriage, but gay divorce that's where the money is.

Trans person files suit litigation money for lawyers. Parents file suit litigation money for lawyers. School doesn't do shit to the obvious socially transgressive sexual deviant and it ultimately results in someone being sexually assaulted, litigation money for lawyers. People can't get trans surgery at 13 so they sue for it, litigation money for lawyers. People regret transitioning in 10 years and sue the hospital for not properly vetting and fast tracking this shit, you guessed it, litigation and money for lawyers.

If there's shit going on and problems caused the lawyers win every time. Why have clear and easy rules that aren't difficult to understand and don't require legal counsel when you can instead have vague and complicated rules that require a lawyer to navigate and then cause additional problems that also require a lawyer to resolve?

And of course who better to write the laws than lawyers.

Not to shit on the whole profession as there's a legitimate need for lawyers and laws in society. But much like the medical profession once profit motive enters into the equation it leads to all sorts of shit.