Tennis players produce up to 3 litres of sweat an hour. A tennis player can create more sweat than their body is able to replace during a 5 hours match, especially when the weather conditions are very hot. Players have to be selective about what balls to put effort into, in order to reduce their own heat and not outdo what their body can take.
You must not be one of the cool kids then.
uhm...no they are not...
If you don't have a a problem with forcing a 16 year old to starve herself while smoking 4 packs a day, you are a real piece of sh#t.