It is implemented in a plainly malicious manner.
Once you find the option buried in developer settings, get past the 2 scare screens and enter your pin it tells you that you need to reboot and wait 24 hours. The two options it gives you are: “Reboot Later” and “Cancel”. Not only is the requirement to reboot arbitrary, not presenting an option to do so immediately makes it seem like they hope you will forget to reboot later and the flow will deactivate.
If you reboot the 24 hour period starts, but there’s no notification when it ends. You are only able to enable the setting for the next 34 hours. NOWHERE before this is any time limitation mentioned, and if you forget about it and come back to it it will not mention why you need to wait another 24 hours.
If you remember in the time window it presents you with the most egregious scare screen yet: 
Your device may be exposed to apps created by developers known to have distributed harmful apps
I find this personally insulting. It’s just plainly defamtory to every unregistered developer. If a supermarket put up an ad that says “If you buy from independent shops you might be exposed to shops known to have sold rotten produce” that would be illegal right?
After that it makes you choose between 7 days and permanent. If you accidentally turn it off you have 10 minutes to re enable before you need to reboot and wait again.
I was able to set it all up and select permanent in one go and had to do nothing after the 24 hours was up?
It took me like 1 minute to do, one time and that was it. I wonder if other phone manufacturers are implementing things differently?
The first time I was forced to do the 24-hour waiting period after restarting, I forgot the next day because life, and then when I went back to it a day later it reset and I had to restart and wait another 24 hours. Only then was I able to turn it on permanently. They’re intentionally making it a hassle.
That’s what I’m saying though. I didn’t have to go back on my phone.