If they can invest in other coins, why can't they buy bitcoin? It's not that they can't afford to buy bitcoin, they're simply greedy and think that bitcoin doesn't bring significant profits so they choose to invest in altcoins. But they need to be careful because not all altcoins will increase in price with bitcoin, the bull season is still very far away and many altcoins will continue to disappear before the bull season really comes.
Some individuals don't have made any investment but they are getting tokens from bounties so they are in hope that during Bull season there tokens will increases in price and they will take profit through this opportunity.
Even if you spend money on potential altcoins, there are no guarantees, so don't count on free coins from a bounty campaign. Things have changed a lot, free coins from bounty campaigns are trash these days. Holding on for long periods of time is pointless.