that may be because when you created your Google account, you told it you were a boy : )

https://chrome.google.com/webstore/detail/adblock-plus-free-ad-bloc/cfhdojbkjhnklbpkdaibdccddilifddb?h1=en

how to help decrease the number of ads:
don't subscribe to every channel in existence! the more you subscribe the more youtube has to pay!

the whole point of youtube is that it's FREE. other apps like youtube exist, but they cost real MONEY every month. Youtube gives you the option of being free but you have to watch ads cause they need a lot of money to maintain that website and to not be taken down by copyright.