We don't really need BTC. I hate when I see people trying to convince others to sell everything they have to buy BTC, it's disgusting. Bitcoin is a lottery, you shouldn't use the money you need to pay your bills and buy food to bet in the lottery right? Bitcoin is kinda the same thing. People should invest money that in case they lost it wouldn't be a big deal you know? It's a long-term investment, however, it's a bet. You can win a lot or you can lose a lot too. Are you brave enough to deal with this risk?
You explain it on a literal way. You are right that we do need need cryptocurrency in our life but it happens that bitcoins is the easiest way for us to earn more money through exchanging it to fiat or working on bounty campaigns to earn altcoins and in this way we can depend on bitcoins to become wealthy in the future.