I can't find the link, but a couple days ago, they said in a thread here it was due to their lack of support of some important security features, and remarked that it didn't look like they were even interested in supporting them.
I hate it when the bad guys do this to my phone
Also if you live in a truly democratic country you don't even need to set the PIN code - your rights are protected by the law.
The problem is not the tracking inherent in the design of mobile telephony networks, which you can circumvent by using burner phones. The problem is for example abuse of tools such as cellebrite to gain warrantless access to your phone at various opportunities.
This is also why proper baseband isolation is important. Baseband firmware is unaudited and likely to have government backdoors.
If the government wants to surveil me, they'll have to put in some actual effort instead of just taking opportunities.
Every mobile phone already is one.