Lets be fair about this. Many parents are using their kids to buy extra pins for them to trade. They are not buying extra pins for themselves. They are trying to make it accessible for those who might actually WANT the said pin. Look at it from that standpoint.
When my GF and I go for BatB, I'm pretty sure we will be keeping all 4 pins we are allowed to buy for her. I'm only there as a way to buy more pins for her (yes my 2 purchases are for gifts to her, but still). In a way, I am like the kids in this example. But at least the 4 pins are not going as traders because we know everyone will be RABID over these pins. We are buying them to keep. (well, unless we have a Ballroom Scene and someone want to trade a Library for it, as that is the ONLY scene she has said she absolutely does not want) Many people are using kids, friends, family, as a way to get a LOT of these pins and resell them or only as traders. Which leaves people who REALLY want the pin at a disadvantage if they don't have something that you deem "worth" the pin you have. You can see the flaws in the system, right?