Reason? Would I be rash in stating the subject of loose set screws and huge problems have been discussed on this forum 100+ times?
This is exactly why I went 100% marine electricals with Quicksilver. When a stick and brick dwelling jumps the foundation and runs off down the road then I put rear view mirrors on it.
But some folks read the advice about removing panel covers and tightening connections and the information leaks out of their ear onto the linoleum.
Tighten the snot out of everything. Breakers need to be yanked hard to proof their tightness. Loose breakers mean annealed contact tangs - replace them or risk a fire.
Sigh. In one ear - on a 4 lane highway and out the other :)