I think in large parts of Europe you need to identify/register when buying a sim. No idea how hard it is to get one without.

Also I was just wondering, albeit maybe ridiculous, if criminals have the same issues with messenger apps as the rest of us, in so far that you are kinda forced to use whichever app is the most popular. I reckon there is not much criming to be done, if everyone in your gangster-circle is using a different app.

I don't think criminals lower down the hierarchies have or have access to much security knowledge, so they might just pick the currently most popular or use multiple apps depending who they talk to.