I didnt declare it was a problem, nor have I complained.I feel like I am repeating myself.
A keg costs 250 GP, and weighs 20 lbs. One dozen kegs is 3000 GP. "Dozens" of kegs is getting to be tens of thousands of GP, and weighs a ton, so isn't mobile in any meaningful sense.
And, as already noted, there's no reason to expect that anyone has such a stockpile. So gathering it isn't easy.
Meanwhile, you have the Necklace of Fireballs, which weighs less than a pound, costs 2000 GP ro so to make. So, I'm not sure I see what the problem is.
For every one of these complaints, we should note: as the GM, you have complete and utter control over the supply of gunpowder the PCs can get. If you don't want them to have it, don't make large amounts available!
I noted that I "thought" the post you quoted was speaking of big explosions and not the effect of firearms.
This has become tense for some reason, so carry on.