~snip~
I am not in the United states, I am way far away from America and in my country to use Fiat as payment is even limited, imagine you want to buy an expensive gadget that worth $6000 and your spending limit on every bank account can't exceed $3000 per month.
If BTC payment become a thing then it will make a lot of sense, I can decide to spend $10,000 per day if I want or can.
Even today, you can spend as much as you want in BTC if you pay someone directly to their wallet. But if you think that an online store will allow you to spend as much BTC as you want without requiring KYC or without adapting to the laws of your country, then you are mistaken.
I have the opportunity to buy almost anything I can think of with cryptocurrencies, but for any amount greater than EUR 1000, KYC is required, regardless of what you use as payment currency.
In addition, we have already been in a situation where many companies allowed payment with BTC, but gave up because there was simply no interest from clients. I don't think anything has changed even today - most people think like
"why should I spend $1000 in BTC today when in a few months that same BTC can be worth $1500 or more?"