"People don't wear them properly."

Yes, spot on anti, got it in one, people don't wear them, or use them correctly. Below is the official government advice on how they should be worn and used.

"wash your hands thoroughly with soap and water for 20 seconds or use hand sanitiser before putting a face covering on, and before and after removing it
when wearing a face covering, avoid touching your face or face covering, as you could contaminate them with germs from your hands
change your face covering if it becomes damp or if you’ve touched it
continue to wash your hands regularly
change and wash your face covering daily
if the material is washable, wash in line with manufacturer’s instructions. If it’s not washable, dispose of it carefully in your usual waste"

And it soon becomes obvious that no-one will be carrying out the correct procedures, it's virtually impossible to carry out the correct procedures and it's sheer lunacy to expect that they will, or can be, carried out by the overwhelming majority of the population, however well meaning they may be. So, as Jenny Harries, Deputy Chief Medical Officer for England pointed out last week, if you can't wear one correctly it's better you don't wear one at all, or you are likely to be contributing to the spread of the disease.

Me, when I go out, I keep well clear of people in face masks, they're dangerous.