My experience is in fact the opposite. I usually buy the larger sets, and have nearly always had left over smaller pieces. It made me worried the first time it happened and I spent the time tracing back through the model only to find I didn't miss anything.
They do precise weighing of bags as a quality control measure. The tiny 1x1 type pieces are more likely to get missed by the weighing so they often add an extra of those pieces to offset a potential loss that might not get noticed when weighing them.
That is why you always get two helmet visors for example when you buy a speed champion. The machine is actually just designed to give you two, because that way if it breaks and misses one, you still have one that you need and it costs them almost nothing to do that. But a missing helmet visor is easy to get missed by the quality control scale. So if you ever buy a speed champion and only get one helmet visor, it is because you lost one or the machine broke. But that's why there's an extra. They do that by design. That's just one example. You see it with magic wands in Harry Potter sets, you always get two, and a lot of sets with 1x1 pieces will always have 1-2 extras just because they are cheap to add in and more likely to get missed in their QA process which weighs the bags.
Every tiny 1x1 piece always comes with an extra. That must be by design.
I think that’s calculated in their cost of doing business. Add one extra of each 1x1 probably eliminated most of the missing parts issue at a fraction of the cost.
> and have nearly always had left over smaller pieces
Almost every Lego set I've ever owned (going back 30+ years to when I used to get Lego) and now my son's Lego recently have all had at least one leftover piece.
