Altcoins are important in there own respect, because you'll have many of them to choose from, i also hear that investors can make huge profit on them on a very short term, also that a coin can become worthless anytime and put it's investors at lose. In that regard i can say that it' more riskier to invest in altcoins than bitcoin.
If we talk about profitability it is true that altcoins can give short term profits but they also have higher risks. The volatility and unpredictability of the altcoin market can lead to sudden price fluctuations potentially resulting in losses for investors. Bitcoin on the other hand has established itself as a reliable and valuable asset over time.
At last the decision to invest in altcoins or bitcoin depends on your own risk tolerance.