Why do people who don’t train seem to think it’s pretty easy to get muscles and hard to lose them? I think what they think is just dumb.
Yes, it does indeed sometimes seem the less that people know about a subject, the surer they are about it.
The opposite of hypertrophy is atrophy and it is much easier to reverse muscular hypertrophy than to instigate it.
Oddly enough, having big muscles is not a fundamental survival attribute in most environments. It also appears to be a pretty metabolically expensive tissue to support. In fact, it has been so important in the past for the body to limit the production of muscle tissue, there are a set of genes that 95%+ of the population carries encoding a special protein called Myostatin, whose only function is to limit muscle growth. Bummer! Bummer big time.
In times of starvation, whenever the body is forced into a fasting state when the intake of protein is suboptimal (as in instances of Kwashiorkor), it preferentially uses this type of tissue first, prior to moving on to fat stores. It is well to remember this next time you want to jump on a crash diet.
If you immobilize muscle, as is the case of a broken arm or leg for which a cast is required, or you are forced into an extended bout of bed rest due to ill health, it is incredible how quickly atrophy is evidenced.
Stroke, paralysis and certain diseases that compromise the nervous system (i.e. M.S., M.E., etc.) have profound effect on muscle growth, muscle tissue support and are major causative factors contributing to muscle atrophy. Oh, yes and don’t forget the disease of Old Age and its handmaiden, sarcopenia.
Just sitting around the house for a little too long while binge-watching G.O.T. and popping the tops off a few too many beers will also usually do the same trick.
Anyway, to finally answer your original question: your non trainers are simply practicing a mindset called cognitive dissonance.