Why do people back these alt coins?

I’ve only started my crypto journey recently, have been trying to learn what I can and have an investment plan I will stick to

$200 index fund per fortnight $200 Bitcoin fortnightly and dumping in lump sums at any dip I can manage

Can some one with some skin in the game explain why Ethereum or another alt is a good investment and where’s the value

Aside from trading over their respective blockchains I don’t think they will ever hold as strong a value and seems like such a gamble

I always see people saying their alt is due to blow up or rocket, but they have nothing to back it up by