They ask to weigh it on occasion at YYZ though I tell them I am in Clase Ejecutiva and then they don't bother.
Never checked in in PTY so don't know, and in MGA or SJO they have never asked, though in MGA my driver has it with him so it would be hard to ask. SJO where I am on my own they have never brought it up.
I suspect on loaded flights and passengers in coach they might say something to encourage checked baggage and more revenue.