That's not realistic though.
LFTs often don't show up until someone actually feels "ill" and they may be infectious before then.
There's lots of reasons why people have mild respiritory symptoms which may or may not be infectious and are often difficult to distinguish.
If I "stayed the fuck at home" every time I had a symptom that could potentially be a sign of an illness that could potentially be infectious and could potentially lead to something unpleasant for a more vulnerable person then between hayfever and bits of sniffles that don't turn into anything much let alone actual colds/ flu/ covid then I'd spend more of the time not leaving the house than getting on with life.
Lockdowns and severe social restrictions didn't eradicate illness and many people have struggled more since then because of the lack of continuous immune updating leaving them more susceptible to constantly evolving viruses.
If you're actually "ill" then resting and recovering is a good thing anyway. DS was ill last week, had a fever mid-week, missed school Thurs, Fri, then it was the weekend so we cleared his plans and with it being a long weekend it was 5 days before he went back to school on Tuesday. I didn't test him; it was a moot point because he was at home recovering for the time required anyway. An LFT may have showed Covid, or it could be a false negative or something else. The brand of illness didn't really matter.
LFTing for every minor twinge just in case you pass it on to a third or fourth party down the chain isn't a realistic or even reliable way to live and the majority of people benefit from their immune systems being able to operate as they are designed to.
Between travel and additional health/ social care restrictions we couldn't visit "Granny" in her final 2.5 years of life. That was a very heavy toll to pay to "protect" her from the inevitable. We managed to go to her funeral.
Minor illness is a fact of life and the costs of trying to minimise that hazard is not worth it to wider society and we're in a worse place in 2022 for it than we were in 2019.