True, I used a fresh one every day during the worst of it, but I have to say I've gone back to doing exactly what you describe. The only place I still need one is public transport and now that it's getting hot (Spain) I often go outside without a coat, so my pocket is the only place to leave it. And it seems like a waste to replace it after one 15 minute ride on the subway.

And I'm not the only one, I've seen a lot of people wearing ones that are all fluffy from long use and sometimes washing (some people really wash disposable masks). I'm sure that will increase shedding a lot.