We can see these days that not all people know cryptocurrencies, if they do perhaps they have heard only about bitcoin, but without owning or having the experience of making any transactions.
Maybe altcoins will become popular within 3 years from now?
So far, I see no reason that alternative currencies would become popular. At the moment, I see only speculation in the market with various coins. I think that in the future they will be in a different form. For example, in the form of securities. And it will really be interesting.
There are lots of reason why alternative currency become popular. They step up the game, did you not notice that some altcoin are popular next to Bitcoin? Many people who are not into Bitcoin are investing to altcoin. Aside from that, these altcoin brings more audience to Bitcoin. So, to some people, they first know a certain altcoin before they know Bitcoin. Dogecoin brings me to know Bitcoin for example.