That's ultimately what it comes down to. Supply and demand.
You want a reliable, affordable source of meat for your snakes? Then "factory" rodents it is, because otherwise people are going to charge far more due to the increased operating costs that would come with making the rats' lives more comfortable, while also decreasing production and therefore fewer rats for everybody. Such is the principle for our own meat as several have already pointed out.
It's unfortunate, but unless you've got the money to support more humane businesses (which, especially in the past year, most people do not), that's just the way things are.