Perhaps they secretly don`t want to wear the hijab,so by sleeping around with loads of guys they feel desired/attractive/loved ?
Well,this hypocrisy is not uncommon. Anjem Choudary was a party animal in university I heard,yet he advocates for sharia law.
Its odd how Islam,with all its restrictions on sex like it can only occur before marriage,yet you read things like harem of women,72 virgins,etc. and you realise how hyper sexualised it is.Sounds very Freudian to me.