To be fair though for the medical inhaler especially, these items require manual input at the basic level and can't be fully automated, so I think it still makes sense to only be available in the craft bench. I'll be honest, It's probably more to do with simply the number of items it takes to make most of the complicated items, zapper, blades, gas mask, basher, all require complex design/input. As I'm sure pressurising a tiny canister does, but the rest of the items, rebar ammo, filter, colour cartidge, are very simple items that barely need any input. Thus I think it makes sense the way it is.
Edited to add;
Also, the inhaler is classed as equipment, none of the other items are, they can't be held and used by the player.
Plus, @mJrA, if all equipment items were available at the work bench, there would be no need for the craft station, and automating all of that kind of stuff seems pointless to me, I mean, once you got them, how many more do you need to make? Unless you die in a place you can't get back to, like the void at the end of the world, you'll never need to make more than one (except the inhaler)