No Free water

My niece went to chicken Licken in Tembisa * sangweni * and I bought two hot wings meal.We went to sit down waiting for our order.My niece was feeling thirsty and stood up to as the cashier for a glass of TAP WATER.The cashier said she will ask at the back and to her return she said they refused and suggested she buy the bottle water.I was so disappointing that they refused to give her TAP WATER especially after we have bought from them.I still dont understand why did they refuse to give her TAP WATER.