system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do people playing tennis wear all white?
gpt
It's only in some venues that you have to wear all white.

Tennis is a classic gentlemen's sport, like golf or polo, so there are some venues that are steeped in tradition, with dress codes, etiquette codes, elaborate rituals, etc.

Other venues either aren't old enough to have been around when these traditions were still in common use, or modernized to try to attract business.