... I believe the reason behind why most people suggest to invest only on Bitcoin here is because this is Bitcointalk and people preferred Bitcoin due to its feature.
Maybe this is the reason, since we are in bitcointalk and most people here just like bitcoin, they are bitcoinists, so we won't see too much altcoins advice here. Honestly, I've joined a few local investment groups on social media, and I've found that most of the people invest mainly in altcoins. Very few people invest in bitcoin because they think altcoins will make them rich faster than bitcoin. And they are all willing to take the risk to invest in altcoins, and during the bull season of 2021, many people got rich quickly by investing in memes, altcoins.