Installers don't need to be licensed plumbers or electricians. A refrigerator is a huge self-contained "appliance" with a power cord that is designed to be inse

Installers don't need to be licensed plumbers or electricians. A refrigerator is a huge self-contained "appliance" with a power cord that is designed to be inserted into a wall receptacle and water plumbing connections that are designed to be installed similarly to a clothes washing machine. You can literally buy one yourself, screw the water connection(if needed) on and plug it into the wall. The only things you should not let the installer do is put a tap on a water line for the fridge or add or modify the receptacle. But provided you've already had a plumber or electrician in to do those things there's no need to spend the extra money to pay a tradesperson to open the refrigerator box and plug it in. And to wit, every single refrigerator I've used has recommended maintenance that nobody ever does, and they have still lasted multiple decades. You don't even actually have to change the compressor oil like they tell you you should.