Additionally, if a homemade mask were to become contaminated, repeated handling could put you and others at greater risk.
Not using a mask as community will ensure that virtually everywhere is potentially contaminated and you are under a larger risk and at all times --not isolated to the moment when you remove the mask (which people typically do at a place where they can wash/cleanse their hands anyway).
So for crying out loud, please stop spreading this nonsense! Masks don't replace washing hands, general hygiene and social distancing, it supplements them. And of course they do work: https://doi.org/10.7326/0003-4819-151-7-200910060-00142 https://doi.org/10.1177/003335491012500206
How does a healthy person wearing a mask prevent contamination?
How do you know they're healthy? That's the key, because asymptomatic cases are estimated to be the main driver of this pandemic by far. And it's only worsened by the fact that only few tests are available.
Nothing short of a hazmat suit will prevent you from catching the virus but all of the above will reduce the chances of you catching it. There aren’t enough respirator, or indeed surgical masks for healthcare workers, never mind everyone else. But we should not let the perfect be the enemy of the good.