I think the major gripe most people have is with a handful of people who were buying 25+ of these limited edition sets solely for the purpose of reselling, while serious collectors were unable to buy any because they ran out. i.e. it's not the selling of them that is the problem, it's the greed involved with those who were hoarding and flipping.
Comes back to a famous saying that's been somewhat distorted over the years: it's not that money is the root of all evil, it's the love of money that's the root of all evil. Greed. Pure and simple.
Unfortunately it seems greed is back in fashion now and seems to be the major driving force behind many people's actions over the past 20 years or so. It's always been around, but we are seriously reaping the rewards lately.
BTW, the "rule" is "maximum 3 sets per household", not just "per shipping address". It's a pretty loose term, but the intent is pretty obvious to limit the sets to any one person or entity. You can always get around everything with semantics (that's how the world manipulates us best).