Maybe that holds true for non-mission critical items. But in the example of blowing up a bridge .. if we need to roll to see if we actually get the explosives, and end up not getting them, we will be in for some pretty silly missions.
That is what the fate points are for. In my first mission I rolled so poorly that we weren't getting ANY gear and munitorium was in fact demanding us to return some of our hand grenades. (no mission gear meant that we would have been walking across a death world rather than riding a chimaera...)
One reroll later we got all the necessary gear and two extra crates which had been left in the chimaera.
Besides, if you are afraid of occasionally getting poor equipment or missing some vital gear, then you shouldn't live in a horribly grimdark dystopia with an cruel and sometimes inefficiant bureucracy. Also, any IG squad that cannot trade/steal/buy/make the missing gear isn't worth their daily rations.