There’s not much point in going out and buying or being persuaded by a pushy salesman into buying a wall bracket when purchasing a TV, unless you are going to hang the TV yourself. If you have all intentions of calling someone in to hang your TV, then let them supply the bracket also.
An installer will be more “in the know” as to what bracket to use and most of the time you’ll find it included in the total job cheaper than the retailer would charge separately. The job would be done quicker and easier if the installer was using parts he or she is familiar with.
I’ve had many clients who bought an unsuitable bracket for one reason or another and have done exactly that, paid more for their bracket than I charged them to replace it for mine. Also if the installer supplied the bracket the installer would cover the warranty on the total job, including parts. I gather people think they are saving money but it can cost them in the long run and is a pain for the installer. It’s cheaper usually to buy a meal than the individual items that make up that meal isn’t it?
Some people do this also, but why would you buy an antenna and get quotes on an installation only? It’s still the same work involved for the installer and you may have bought, once again at retail price, a substandard or unsuitable antenna. If your antenna broke down the installer won’t have to warranty it, you’d have to pay the installer to remove and replace it again it wouldn’t you?
So the golden rule is only buy parts if you can do the full job yourself.