Tourism is a large industry in the UK, and Royal destinations are some of the most significant tourist sights, e.g. Buckingham Palace, Windsor Castle
Many people are attracted to the UK for its history. The Royal Family is an important part of that, and many people want to visit the places they live. There is a special appeal in that the Royal Family is not just historical, but still functioning today. The British monarchy in particular is famous as being one of the most longstanding, and is famous the world over. This means many people come to the UK and spend money because of the Royal Family, which employs people and contributes to the economy significantly. Abolishing the Royal Family would mean a large drop in tourism, as one of the countries most unique and interesting attractions would be gone.
Many of the things people come to see could exist without the Monarchy, such as Buckingham Palace (which only opened its doors to tourists relatively recently in the wake of public opinion turning against royalty) and the changing of the guard. Chester zoo, Stonehenge and the Roman baths in Bath are equally as successful tourist attractions without a royal theme according to UK national tourist agency. The Palace of Versailles continues to generate revenue in France without a monarchy . If the Royals were no longer in residence, these could be opened more and generate more revenue.
[P1] The Royal Family generates money and business for the UK economy. [P2] We should keep the monarchy as it benefits the economy.
Rejecting the premises
[Rejecting P1] Economic benefit alone is not a reason to keep something if it causes other problems. Additionally, there is no evidence that the monarchy generates more income than the annual 300 million pounds it costs per annum.