Because Banks in Britain and the United States have banned the purchase of cryptocurrency by credit card. This is bad news makes bitcoin and cryptocurrency market are going down. 
This is a good thing. People shouldnt be able to invest in Bitcoin with credit - money they dont have, which inflates the price, creating a fake price built around debt. This is not good for the long term of Bitcoin or crypto market as a whole. I think the banning of credit cards is a good move which may drop the price initially but will help to drive the price to ATH's in the future.