Speaking from experience, no, they really don't.
As LPL will tell you, you don't need to have the most secure thing on the planet, you just need to be a hard enough target that the thief gives up or picks something else.
If you don't lock your bike, sure it'll get stolen from some places.
Bike theft is a crime of opportunity. Nobody is stalking a specific bike to take, it's usually "oh shit there's one that looks easy imma take it"
I have a hardened steel U-bolt lock and a thick AF cable (do not get any cables under 1/2in as they can be easily cut with side cutters or even good wire strippers) the U lock goes through the frame, the cable and disc lock go through the wheels as well. I also like to take my seat with me in my bag, since nobody wants to ride a bike without a seat.