I would suspect that the reasons for that are as follows:
a) a particular business may advertise on this site
b) as a whole, the business may be doing a good job of providing their paticular service or parts, etc.
c) to label any business as one others need to avoid due to one customers bad exprience is just not a fair thing to do.
I run an auto repair business, and one thing I have learned is....there will always be a customer that you just can't satisfy, for whatever reasons
And.....there will always be a particular vehicle that just gives 'fits' to get the repairs done quickly and properly, and within the estimate.
There will come a time in some repairs that you just have to say "enough".
Those are the ones that no matter which way you turn, everything goes wrong.
I have come to believe that those are due to the owner's having "bad luck", and now "I" have to be a part of it. You just wish you had never started the job, and that they had gone somewhere else.
Losing $$$ on a repair is just not condusive to a successful business.