I don't think we do pay for as many of them as is generally assumed.
There are changes afoot, but the money the Queen receives from the Civil List is in exchange for the income from the Crown Estates, which was surrendered to the state by George III in 1760. Before that the Sovereign was personally responsible for the costs of civil government.
"Only The Queen officially receives direct funding from the Civil List. The Queen's consort (Prince Philip, the Duke of Edinburgh) receives £359,000 per year. The Queen, as Head of State, receives £7,900,000 from the Civil List to defray some of the official expenditure of the Monarchy.
The state duties and staff of other members of the Royal Family (but not The Prince of Wales, The Duchess of Cornwall, The Duke of Cambridge or Prince Harry) are funded from a Parliamentary Annuity, the amount of which is fully refunded by The Queen to the Treasury. The Queen is permitted to claim this amount as a deduction against her gross income from personal investments and other sources - the net amount, after deductions, is subject to normal income tax." en.wikipedia.org/wiki/Civil_list
The income of the Prince of Wales comes from the Duchy of Cornwall, which has been the property of the monarch's eldest son since 1337.
"since 1993, the Prince of Wales has voluntarily paid income tax. The prince paid a voluntary contribution to the treasury of 50% of his duchy income from the time he became eligible for its full income at the age of 21 in 1969, and he has paid 25% since his 1981 marriage" en.wikipedia.org/wiki/Duchy_of_Cornwall