Why would anyone oversell?

I just don't get it - I mean everyone has been over sold to right? Everyone knows how it feels so why do people do it? It's so short sighted...

In business you need to be in it for the long run. Never never over sell - and in the 10 years or so that I have run this business, I have and never will over sell to ANY customer.

I remember being over sold to and I never went back to that shop as I knew they were trying to fleece me! It sucked, and they knew it.

Treat others how you want to be treated yourself right? Simple - or is it...

Rant over