People are more pose to trading bitcoin than altcoins because of many bad experience about altcoins. Recently many traders got a bitter pill of altcoins after they failed to perform like we saw the bitcoin did, so many are careful to stay close to bitcoin in other not to miss out of gain.
I think altcoins are still profitable, so far we can see the price of altcoins continue to follow the movements of bitcoin which when altcoins fall then it is the right time to buy and when bitcoin prices rise then the price of altcoins will also increase as it has recently, if this is done well I'm sure we can still make a profit from altcoins.
what you are telling is good for only short term trading but if you want to keep altcoin for long term then surely you will be in loss. altcoins are controlled by the developers and are depended on the projects development and its success. but bitcoin dont depend on any projects or anything it is just like currency which is used by other altcoins