The idea is protection from crime. You can have the window tilted and thieves theoretically cannot climb in through that window, where a swinging or sliding window while open allows someone to climb in through it

Of course in practice they’re less safe where they’re popular as there is a tool, a hook, which allows someone breaking in to hook the handle, pull the tilted window shut, and open it again in swinging mode, allowing them in

My understanding is sliding windows are the easiest to secure as you can bolt lock them at any point of openness. My sliding windows have bolt points at closed and at 5cm open