People who can afford to pay will take up valuable GP time solely to gain a free prescription for drugs that are available cheaply (e.g. Paracetamol, costing only 49p for 16 tablets at the supermarket). I have even known them to then give these drugs away to working friends and family. This waste of GP time deprives genuinely sick people of opportunities to get the attention they need and results in excessive cost to the NHS and the tax payer.
Pensioners and other non-means tested benefit recipients are entitled to free prescriptions irrespective of their wealth. Unless they are on means tested benefits, they should not receive free prescriptions for low-cost medicines available over the counter.