Take a look at the Currys facebook page, it is nothing but negative comments, literally every single thing Currys post on their page has dozens of terrible customer experiences tagged to them, it's hilarious. Shocking company. I'm amazed they actually let customers comment.
Confirmation bias.
It is so normalised to moan, whinge, and complain.
Not so to give credit where it is due.
If you offer a genuine "thank you!" or word of praise, it is not uncommon to be looked at like you've gone out, or have two heads.
That, and the default position being to complain, probably makes negative experiences appear to make up a larger proportion of transactions than they actually do.