let me say that we don't have the resources to test printers in the way you describe - printing and then waiting days (weeks?) before printing again. That's not the object of the exercise in any event.
The printer tests are designed to examine the build quality, print quality, and print speed of the machines, using carefully selected files to test the printers' capabilities. That's what we believe our readers want to know. Contrary to what you say (and I'm not sure what data you have to support your statement)many computer users do use their printers on a daily basis, and even if they don't, we're not aware of a huge number of people who have had the same experience as yourself. Blocked print heads are almost always the result of printers standing idle for long periods, and there's not much that we can do to detect that in individual test machines - short of having a lot of printers standing idle for long periods. Manufacturers aren't going to provide us with test models on indefinite loan.
I have used printers from HP, Canon, Epson and Lexmark for years - sometimes heavily, but at times sporadically and I can honestly say I've only had a blocked printhead once. That isn't to say the problem doesn't exist - you're living proof of that - but I don't personally think it's a widespread and serious concern; if it was, the manufacturers would address it. An individual model may exhibit a greater tendency to block, but I can't remember there being too many threads on the subject over the life of this forum.