Because no governing body cares about the proper care of a tropical fish. Many people still have the mindset of flushing a dead fish down the toilet as a normal disposal method. If that was a puppy, or kitten, people would lose their sheet. Like I said previously the regulations regarding pet fish in the trade, including food, etc, are lax, and always have been. If around the globe a few million wild fish die in the collection process, oh well, if 10's of millions die in a LFS after being netted and shipped from all points on the globe, umm, so what. If 3 dogs die due to what some consumer feels is a tainted bag of dog food, class action lawsuits are filed. It's just a reality, tropical fish have almost zero value to most people, including the vast majority that shop at big box stores. Just ask GS how that plays out at the Petco that he works at.
So while discussing possible regs and rules and/or potential size restrictions etc about tropical hobby fish sold at the LFS, or online, is all good and well, it's just fantasy talk that will never result in anything, unless those tropical fish come under the invasive species magnifying glass. That's when bad things can happen, with real consequences that are already taking place and that are already affecting members of MFK.