This seems sensible. LFTs, while not infallible, are a good indication of infectivity. Most people aren't thought to be infectious after 5-7 days, and those who are will mostly be picked up by day 6&7 testing. It seems better than trapping large numbers of the workforce at home when they are well, just in case (and why stop at 10 days, someone somewhere might be infectious after 12, 15, 30, etc?).
In any situation there are going to be some outliers, but as PP say, it's probable that the few who continue to be infectious after 7 days are vastly outnumbered by the people who are out and about infectious before they even realise they have symptoms, never mind test.
The people who don't test, or lie, or go to work when they don't feel well are always going to do those things, regardless of changes to the regulations.