Its not just because they are useless, if they said, 'ooh i dont know, i'll just find out for you' that would be fine but they aren't allowed to do that.

I very briefly worked at a very well known UK chain of petshops and I had no training what so ever, literally everything i knew came from my experience with my own pets, so there were a few times when i didnt know the answers especially as they used to move me to different departments every other day. Anyway one day i got caught telling a customer that i didnt actually know but would find out for them and the manager started yelling at me after they left because the golden rule is 'if you dont know, make it up to make a sale' 2 days later i got caught telling a customer that you cant keep 2 male syrian hamsters in a cage together and was yelled at for that too, apparently golden rule number 2 is 'never discourage anyone from buying anything because once theyve paid for it its not our problem'