networkn:
Tyre dealers who tell you the tyres on your car tyres wouldn't get a warrant and should be replaced immediately, second opinion from another professional with measuring device shows they aren't anywhere NEAR as bad as that and probably have 3-6 months driving left on them.
My mechanic, with whom I have a longstanding relationship and whose judgement I trust completely, explained to me that it is a safety issue. Tyres that are worn but still legal don't grip as well or stop as well or drive around corners as well or handle as well in the rain. They may not be illegal, but tyres with only 3-6 months driving left on them are definitely not as good as newer ones would be. Usually you only discover this during an emergency.