Why cars in Britain arent usually equip with automatic transmission?

That is not only true in Briain, the entire Europe too. In fact, in many places outside of the US, manual transmission is most popular.

To save fuel mainly, among a few other reasons. You might think gas is high here in the US, but wait until you fill the pump in Europe.

Europeans drive cars; Americans ride in them. Often while eating or using a phone, not that no other culture does that.