People will of course prefer Altcoins for the reason prices matters but some investors convert their profits into Bitcoin rather than holding it all in Altcoins which is pretty risky compared to Bitcoin. I don't think Bitcoin is fading out and losing popularity because it is now the new play ground of some institutional investors.
Not all people! People with no money will prefer altcoins because they'll at least feel they have a share when they invest 100 dollars in some altcoin worth a few bucks. This isn't a smart move if you think about it.
What would you rather have? 1 gold coin or a whole bag of copper coins? Although you could say that the probability of those copper coins gaining value is the same as with that gold coin but gold is always easy to recognize and easy to value, like bitcoin. Everybody knows what bitcoin is but try to ask someone if they know what Waves is and how much it is worth. They'll have no clue.