Loctite is typically known for its thread lock “to keep bolts from coming loose”, but Loctite make a lot of different products. Anti-Seize make a thread locker (same as Loctite) but it typically is known for its anti-seize grease, used to keeps parts or threads from seizing up or rusting together. I hope this helps.
Loctite brand makes an antiseize product as well.
anti-seize is used when you are using a bolt in a place with two different metals so they dont get fused together over time (example- installing stainless bolts in your aluminum motor)
it is also useful to apply when you are using a torque wrench to get an accurate torque without the friction
There are several loctite products. Make sure you use the right one, or you may find yourself unable to disassemble a part! Usually, the blue is good enough. Stay away from purple unless you know what you are doing.
I've been a machinist/maintenance machinist for 28 years. If I don't loctite something on my bike, I never-seize it. Screws like a little lubrication when you are putting things together, keeps them from seemingly welding themselves in, especially in a corrosive environment or like someone mentioned above, different materials between the screw and the cases, or whatever they are going into.