Sure but what if the US govt decided to launch a 51% attack on btc anyway?

I don't argue that blockchain tech will keep improving. I just say if it's going to be a currency of the future why do we have to spend money on it now? Won't we be able to create parallel blockchains to increase token supply? It's not an intrinsically valued asset, like buying a stock (which some have returned more money than speculative bitcoin purchasing). Why should the bitcoin believers tell everybody to buy it if there's nobody accepting it for payments?