Besides bitcoin we can choose some coins to invest from altcoin.
Yes, only some because not all of them are worth to invest with our money. Most of them are just typically pump and dump coins.
But investing in altcoin is more risky than bitcoin. Again bitcoin's If you invest in altcoins, you have the opportunity to make more profit.
It's true that they're riskier than Bitcoin. We hold Bitcoin and invest some if you want to but you have no idea if they're going to make it when the bull run is in.
Bitcoin is more appropriate for most and that's why if you ever want to have a safe and secured investment, Bitcoin is the choice.