What you are not hearing is that vaccines are highly effective, but not 100%, and tests are very accurate, but not 100%. There is no 100% to be had.
When rates of infection are high, it is sensible to take additional measures such as masks and distancing. When rates of infection are very low, it makes sense to dispense with them because your risk of encountering someone who is infected and catching it and passing it on is already vanishingly small and , let's face it, those things are a pain.
Unless Covid is eradicated, there will always be a teeny tiny miniscule possibility of meeting someone you could catch it from. It just won't be worth doing anything about, until numbers start to rise.
The point of the vaccines is a) to protect the individual who has it and b) to drive down the rate of infection, so that we reach the point where we can abandon distancing. BUT WE ARE NOT THERE YET.
The point of LFD tests is to identify some asymptomatic people who would otherwise not be identified, so they can isolate and avoid passing it on.