Perhaps set size is a contributing factor? I've bought two sets over the last few years, and both of them have had a piece missing. One was 1969 pieces (no prizes for guessing which set that is!) and the other 1222 pieces.
Both occasions the pieces weren't structurally important, and were small decorative elements.
I've put together probably 50 sets over the past 5-6 years. I pretty much only buy the largest sets they make, especially Technic. I doubt I have many sets under 1500 pieces.
I've yet to find a single missing piece so far. Many times we thought a piece would be missing, only to find it trying to escape somewhere. The plastic bags carry a pretty heavy static charge in dry winter conditions, and the tiny pieces love to stick inside those in the corners where they somehow turn damn near invisible.
To be honest the quality control is pretty unbelievable. If someone tells me they had 6 sets with missing pieces over the past 5 years my initial reaction would simply be to not believe them as it's so easy to misplace a piece during a 2,000+ piece week-long build. I've misplaced dozens to the point of having to order replacements from ebay or whatnot - only to find the pieces lurking around my house before the new parts even arrive. The joke of the household is you need to order a replacement part and then you'll find what you're missing a few hours later by complete accident.
I've found pieces in the strangest places. If you accidentally sit on one they will basically become one with your flesh, and I've found random pieces floating in the tub completely unexpectedly.
Knocking on wood my luck (and Legos QC) continues.
I have the exact same experience as you. I have build 50+ sets, 10 of them 1500+ piece sets and a few over 3000. I have never had a missing piece. I have had small pieces that was hiding or I dropped on the floor, but never missing. There is always some additional pieces in the set, and I assume it's because they err on the side of being sure.
I have opened and built hundreds of lego sets over the years, and the only missing pieces I’ve ever had were in the Saturn V set. I think they had a QC issue on that set specifically.
Both occasions the pieces weren't structurally important, and were small decorative elements.