Cause altcoins are the way to earn more money than Btc. In this case, bitcoin is safe but will return low profit but income from altcoins could be more ,will cross btc. Even altcoins coin manay variable. Some altcoins may risky but potential altcoins also available to ensure your income. pump and dump is natural here but if you can choice good altcoins at perfect time, then it could be huge. That's force people to increase their interest altcoins
altcoins are also often chosen because they are often cheaper and very accessible. And yes, they can bring more profit if the market allows this, which is why many beginners first focus more on altcoins.