Actually both Bitcoin, shitcoin, altcoins etc are all embedded in Cryptocurrency but because of the potentials Bitcoin has over all other coin, we have to address it different from other cryptocurrency and we ought to specify Bitcoin whenever we are talking about it so that newbie won't go and invest in the wrong place and I believe these are the reasons we should not..., maybe when those other cryptocurrency prove themselves they can also be set aside as Bitcoin but until then Bitcoin shouldn't be address as cryptocurrency because there is more to Bitcoin than those...
Indeed bitcoin is now a father of all coin in the market but that does not change the fact that bitcoin is a cryptocurrency, we still have every right to describe it as
cryptocurrency so anyone that is using the term Crypto currency"
is not wrong but when we are making use of this term
Crypto currency" it means that we are referring to all the coin that is present in the Crypto market. So anyone that is giving reference need to be specific to enable those who are not familiar with this term to know where they are heading.