I believe QTing animals is a very smart thing to do for several reasons and something I practice as an individual....but like many things in life it's a choice. Not to defend not doing it but there are several ways to lose an entire collection besides QT that I don't think everyone does:
Redundant thermostats (in case one fails and frys your animals)
Backup generator (for power failures in extreme temperatures)
Tabs or conduit on cages to keep cages closed if one should escape and open other cages.
An escape plan including snake bags and boxes for every animal in your collection should a fire/disaster happen.
Escapeproofing the 'herp" room
I'm sure there are also more I'm forgetting.
All of these things to me carry potential to lose a portion or all of one's collection but as an individual we have the right to choose which, if any, we want to practice.
As keepers I think it is great that we can pass our experiences and information onto others to help them and educate them about the risks that they could be taking by not practicing certain husbandry techniques. BUT it is their choice to practice those techniques or not. Some people are riskier individuals than others and that is their choice.
We as buyers can ask about these practices and weigh our decision to purchase based on these techniques just as we can choose what to do after we receive an animal.
I'm not trying to be preachy but the best method IMO is to educate the community and politely inform them of the potential risks that they run from certain practices (or the lack thereof). If they choose to heed that advice or not is completely up to them.
Hope that helps
