Why not use SIM?

SIM is good, it let's you connect to your friends etc. but it has some problems with your privacy.

SIM is just like a mini computer with it's own operating system. You can think it's good but it's not.

First of all, they can find your EXACT location with triangle method. If there's three cell towers, they will calculate your distance to them and find you.

But, how can they find your distance? By using Silent SMS's. It's an SMS but it's designed to hide from you. That's why they are really dangerous. They can do a lot of things like finding your distance to cell towers, exploting zero-days and many more.

And, they can create fake cell towers. They make you to switch to 2G and they can listen to it really easily because it doesn't have well encryption. If your phone has full network but it's 2G, you're under attack.