This is the real objection, and it is rarely said out loud. People have read that heat pumps do not work in old houses, that you need underfloor heating, that the radiators all have to be replaced.
Some of that is nonsense and some of it is fair. An installer who writes plainly about which properties suit a heat pump, which need work first, and which are honestly better off with a boiler for now, is the one people trust. Saying no to some houses is the strongest possible signal that your yes means something.