I did ~40 NM runs yesterday and didn't even get my 2nd weapon. If this was 5%, then I don't want to know what 2% feels like.
Math alert!
40 runs and 5% - 12.8 % chance to not get drop after 40 runs.
Now let take 2% - 44.5% chance to not get drop after 40 runs.
The lower % chance is, the less this common "sense" of probability (which is wrong from math point but some ppl think it's working)that I after each 50 (using 2%) runs I would get an item works.
When you take 50% chance and think about it as success every 2 runs you have 25% chance to get 2 fails in row
When you take 2% chance and 50 runs (so with the same proportions) you have 36% chance to get 50 fails in a row.
It's even called a problem of low probability on many papers. The lower single probability is the higher chance for "backluck" streak is.
When you take thousands of players, on average on those thousands of games 2% of them ends up with drop. When you take single player, one can easily end up with few items after several runs and other can have zero after even hundred of them.
You can say that on average with huge amount of games this would be the same, but the problem is that those who get lucky, won't farm it more (because they don't need it).
It's like lottery. In theory with enough games going to infinity you should win at some time. But there is no point in winning after spending 3 times value of reward for tickets, that's why only those "lucky" at start wins truly.