Bitcoin need altcoins because most altcoins are traded altcoin/bitcoin so using bitcoin is going to be more and more often but also when some pupils earn money by trading on some exhangers where you can trade your altcoins you can invest your bitcoins in site which accept bitcoin and earn more bitcoins so I think that the biggest reason why bitcoin neeed altcoins that there are more and more bitcoins and more market capital bitcoin have because some kind of new cryptocurrencies.I also think but only think that China is creating new cryptocurrencies to push bitcoin price up when traders trade with altcoin/bitcoin cryptocurrencies.So If that what I tell is true then that is perfect strategy created and good for everyobody here.