If you are familiar with the stock market, you probably know the concept of penny-stocks (i.e. stocks that trade for less than a dollar). These stocks are particularly risky. And particularly interesting.
While the bigger stocks may represent safety of your money, they can also be quite boring. These are the types of things that your financial advisor would recommend you to buy. And she would be right.
But when it comes to altcoins, investors (speculators) are not there for a 10-20% growth in a year. They are there for 10-20% growth in a DAY. And while the known suspects of bitcoin, ethereum, and so on did have those golden days of massive growth, they are the "blue-chips" now.
If you want to experience the thrill of massive gains (and losses) in a single day, go and have a look at the lower part of the market capitalization list of cryptocurrencies (here -> https://coinmarketcap.com/). You can find some interesting things in there.