Why do all public swimming pools have a life guard?

Answer 1

Because public Swimming Pools are run as a business. In business, the owner and staff have a 'duty of care' to ensure the safety of everyone on the premises.

The life-guards are there to rescue anyone who gets into difficulties while using the facility.

Answer 2

Because - not everyone who uses a swimming poll can swim! While you're using their facilities - the pools owner who has a 'duty of care' to ensure you use the facilities safely.