Tennis was a spectator sport, which meant a great opportunity to show off your skills and to gamble! Both players and spectators could bet on the outcome, with the privy expenses showing that even the King could get it wrong. Between 1493 and 1499, Henry VII lost a total of £20
Yeah. Even the king lost money betting on tennis.
https://onthetudortrail.com/Blog/resources/life-in-tudor-england/tennis-in-tudor-times/
They kept trying to ban it in the city of London.