I think the problem with people wearing glasses not specifically tailored to then for extended periods of time is that it can damage your vision because your eye muscles are having to work harder to compensate.
If you have other things like astigmatism which can be different in each eye, then a correct prescription is vital.
100% agree with what you say. However, if it's just simple age related difficulty with reading, then a pair of cheap reading glasses are perfectly satisfactory.. I got my first pair of reading glasses over 25 years ago. They were prescribed by an optician and the private eye test in a foreign country represented a fairly large outlay. The Optician himself suggested that, for me, cheap reading glasses from the pharmacy would be a better option.
Since then, over the last 25 years, I have found cheap reading glasses sourced from quality outlets [a pharmacy] to be perfectly satisfactory. As I pointed out when I joined DBUK back at the end of April, one of the many health indicators that forced me to come back on to the grid was that, starting around last Christmas, there has been a significant deterioration in my eyesight.
That last is the key point: If cheap reading glasses are going to work, they will work well. If, on the other hand, the results are less than satisfactory and you are still having vision problems, then you need an eye test and
must see an optician.
While left of centre in political outlook, I am actually a libertarian, and firmly believe that, everything else being equal, people are quite capable of deciding whether cheap, off-the shelf reading glasses are solving their vision problems or not.
Completely off subject by the way, but as someone who has identified as being 'Libertarian' since I read
Kropttkin in1970, I am deeply offended by the way libertarian ideology has been hijacked by the right.