Well, we all suffer of some biases, and focus only on the things we are confortable with.
Altcoin may be are profitable, but they are too unpredictable to invest in them.
Most of the altcoins who are in the top spot did gain so much increase in their prices that's why bitcoin dominance almost fall to 30% which if I recall correctly bitcoin dominance last year ranges from 60 to 75% observe that if you're going for altcoins beside bitcoin, you gained so much from your initial investments, that's correct as some people are not knowledgeable in altcoins, they just knew bitcoin which is given by its popularity and potentials. We've missed a lot of rockets these days.