I suggest you download this document from the World Health Organisation dated 5th June:
https://www.who.int/publications/i/item/advice-on-the-use-of-masks-in-the-community-during-home-care-and-in-healthcare-settings-in-the-context-of-the-novel-coronavirus-%282019-ncov%29-outbreak
It is a comprehensive document which explains the pros and cons of face coverings. If you can’t be bothered, here’s a few salient passages:
Advice to decision makers on the use of masks for the general public:
Many countries have recommended the use of fabric masks/face coverings for the general public. At the present time, the widespread use of masks by healthy people in the community setting is not yet supported by high quality or direct scientific evidence and there are potential benefits and harms to consider.
Potential harms/disadvantages
The likely disadvantages of the use of mask by healthy people in the general public include:
• potential increased risk of self-contamination due to the manipulation of a face mask and subsequently touching eyes with contaminated hands;
• potential self-contamination that can occur if nonmedical masks are not changed when wet or soiled. This can create favourable conditions for microorganism to amplify;
• potential headache and/or breathing difficulties, depending on type of mask used;
• waste management issues; improper mask disposal leading to increased litter in public places, risk of contamination to street cleaners and environment hazard;
• difficulty communicating for deaf persons who rely on lip reading;
This bit is particularly interesting:
WHO offers the following guidance on the correct use of masks, derived from best practices in health care settings:
• perform hand hygiene before putting on the mask;
• place the mask carefully, ensuring it covers the mouth and nose, adjust to the nose bridge, and tie it securely to minimize any gaps between the face and the mask;
• avoid touching the mask while wearing it;
• remove the mask using the appropriate technique: do not touch the front of the mask but untie it from behind.
• after removal or whenever a used mask is inadvertently touched, clean hands with an alcohol-based handrub, or soap and water if hands are visibly dirty;
• replace masks as soon as they become damp with a new clean, dry mask;
• do not re-use single-use masks;
• discard single-use masks after each use and dispose of them immediately upon removal.
Everybody doing all that? No, thought not. The miniscule - unproven - advantages of widespread "amateur" wearing of face coverings are immensely outweighed by the risks from improper use as detailed above. I personally will not expose myself to those risks as I certainly do not adhere to the required safety measures.