This is just weird. From the BBC:
Easyinternetcafes - owned by Stelios Haji-Ioannou, the founder of low cost airline Easyjet - claims the headgear is linked with "deviant" behaviour. ...
"Since deviant behaviour can be associated with the wearing of baseball caps we are politely asking people who enter our premises not to wear caps.
"This policy is designed to combat anti-social behaviour such as theft."