I understand realistically that bear traps and mines would be quite heavy, and make sneaking difficult (I made the bear trap heavier because realistically it would be heavier, but gameplay wise it is actually much weaker than a mine, and should really be lighter).
But it doesn't work out like that, currently you can carry half a dozen mines and say 500 SEC and you won't lose any sneaking skill at all, you just have to recharge your stealthboy every 2 minutes until you find a place (or person) for storage, which is excessively wasteful unless you are very concise and specific about what you want to do. I'm happy for realism to take a back seat to gameplay in this area, as I said it is a very specific reasoning for the change being that it is only really sneakers effected by the weight system now.
For any non sneaker the weight of traps isn't an issue, they could carry 15-20 if they wanted to, with no penalty, able to set them all up quickly and without interruption, a sneak has to run back and forth between his storage location and set mines 1 by 1 unless he has an unlimited source of SEC.
With the no skill FA kits and doc bags, it is a similar situation, it makes sense that gameplay wise, someone who is sneaking and using doc or first aid, would be at some degree of advantage if he had the skills needed to do so. So someone with only a very high sneak for example (and low FA/doc), would need to carry the more expensive and heavier version of the kit to maximise his healing output, reducing his options for other gear.
Once again I know this is very specific to sneakers, but I don't think sneak weight was considered when most items were given a weight value, as it wasn't important, but now with the SEC cost of sneaking being modified by weight, some items that sneakers need/want/can utilise need a bit of a weight workover.