Wearing rifle-rated body armor seems like the most obviously beneficial daily practice. In addition to stopping bullets, it also protects from bruises and abrasions. It’s such a great idea that it should be mandatory!
Oh, wait…why not? Armor, even the best and the lightest, is still heavy, still restricts air circulation, still puts extra weight on the spine and the leg joints. It’s a great protective measure for certain environments but, even in wartime, many troops choose not to wear it. They win in mobility and endurance, or in the ability to carry extra ammunition for the same weight. People whose roles require wearing armor for years, especially if they had to run in it, usually suffer from back problems.
The same trade-offs apply to masks, both to the effective types like the one above and to the ineffective improvised craft projects. In theory, they restrict the transmission of viruses through restricting incoming or outgoing air flow. In practice, most of the do not work well. If you can still smell cigarette smoke or kitchen smells through the mask, it’s not working against viruses.
The trade-offs are the restricted airflow (reduced endurance, asthma attacks, heart attacks, other health problems) and the contamination of the inside surface with bacteria. That bacteria gets to live in a warm, moist environment perfect for reproduction. Increased acne, rosacea, other types of skin inflammations thrive under masks. The harm done by those side effects far outweighs even the theoretical benefits and is only slightly mitigated by non-compliance.
Free people should be able to make their own choices. Forcing masks, especially on people whose physical or mental health would be immediately harmed by them, should be considered a violent felony and stopped with appropriate measures. Unfortunately, in many jurisdictions, police enforce those edicts against the general population while giving the politicians a pass.