Lost over time? Worn out or broken?
If canteens and mags aren't getting lost and worn out, neither are compasses (something that is specifically tied of to you by design rather than fieldcraft). And neither would your coat if you've got your rucksack and rations. Same with the rest of things that should be with your ruck. Maybe one or two are gone, but the whole team's e-tools? With no replacement to pull out of Bob's bag when he got smoked a few weeks back?
And, yes, 4e is assumed to start in the aftermath of Kalisz (or its Swedish equivalent). Earlier versions are totally focused on breaking out from Kalisz, with that being the starting scenario included.
I don't actually see canteens listed in equipment, other than in the bit that states ". In addition to the items you choose, you are assumed to have a uniform or sturdy civilian clothing, and a canteen for water".
It states "rations of water", but those could be in used plastic soda bottles or whatever else the players have scrounged up. And the magazines might not be the ones they started out with, it's just stuff they've picked up off of dead bodies or whatever.
However, from the way you're writing all this, it seems you assume that all the players are from the same unit. you keep saying things like "the whole team's e-tools" and "no replacement to pull out of Bob's bag when he got smoked a few weeks back".
Sure, they're all part of the 5th (or 2nd if in Sweden) if you just go off the default start setting, but that's still like 17.000 men in a division. And the players are 5 or so of the survivors.
And they're on the run after a disastrous battle. And that battle was launched after a very long time of attrition.
Like it says in the flavour text on p30 of the referee manual: " You were a raggedy-ass division - half of you on horseback or foot. Vehicles running off distilled alcohol. Uniforms mended, then mended again and half of those from other units if not other NATO countries."
But you're looking at the situation as if this was a completely fresh unit with full stock of equipment and supplies that accidentally wandered into a bad situation and ran away.
Most of the shit you don't have on you, you lost long before the battle of Kalisz. I'd imagine that since the supply lines broke down 2 years ago, a lot of the equipment broke or got lost and couldn't be easily replaced.
I'm betting they were lucky if they had one compass and map per platoon, let alone squad or individual soldier.
Same for a lot of the other stuff.
(I do believe that your coat is assumed to be included in the "you get a uniform or sturdy civilian clothing" statement for starting gear).
But hey, if you're the GM and you want all your players to be from the same unit, and you want them to have a full supply of equipment despite years of having no supply lines and constant wear and tear, go ahead and give them that.