It's because I'm noob? :lol God. No, I had it happen once on stalemate (and the Pyro ran up to do it after I started Engie-dancing, before I saw him), and once when the other team lost and the Pyro snuck up behind me, while I was looking down an exploded hole in a Payload map to grab a screen. 98% of the other killing tools don't work once the round ends, why should the failing team(s) get to keep that weapon?
Stalemates were always about running up to the other team and reveling in the "lol, we suck" moment because neither team won, and the game boos us all. Why should I have to be extra careful and paranoid if they chose Pyro or Heavy, versus the other classes?
C'mon, don't fall into the "cuz ur a noob" bullshit.