Poor Service

I went to Woolworths at Sammy Marks Square in Pretoria. I bought groceries and the cashier informed me that trolleys are not allowed to leave the shop. He then offered to help me carry my bags sine they were very heavy to the under parking only if I asked the manager in charge. The Manager refused and told me that they are short-staffed. My question is, why are we not allowed to take our groceries using their trolleys and why do they sell groceries if they don't have people to assist with trolleys? I was very disappointed with the response I got from the store manager