some people dont sell bitcoin to buy products via their domestic fiat currency. some people instead sell bitcoin at a high, to a stable token to use as their own reserve. to wait out a correction to then accumulate more bitcoin at the correction low (buy low sell high repeat)

if we consider domestic inflationary fiat as "burn money", something not to hold onto for long but just use temporarily and get rid of as fast as possible for convenience.. then:
some people do sell bitcoin on a high, to maximise how much burn money they get, to then buy as much products as they can, which is a better idea than to just hold only domestic currency long term without ever having used bitcoin, whereby from date A to date B the person would get less products not more

some people want to save their value they earned from employment which as second scenario reveals is not good to hold that value in domestic fiat, due to inflation. so hedging that inflation by storing value in deflationary asset solves the problem

with those things in mind. it must also be noted that trying to displace a domestic currency and replace it with bitcoin would end up with a government adopting bitcoin too much to then set superfluous rules and draconian rules on bitcoin users which then ruin the advantages of bitcoin.

bitcoin is not meant to replace domestic currency for everyones day to day spending. its suppose to hedge against the inflation of domestic currency. it is suppose to give people a different option, a exit, a side store, away from the domestic currency system

...
let me explain my experience over the last 13 years of being a bitcoiner
im at a stage now where i sell a portion of my bitcoin hoard near each 4year cycle ATH. and i collect my burn money. i then pay utility bills upfront(ahead) so that im in credit, meaning they owe me credit for utility services instead of me owing them monetary debt every month

this alone has many benefits:
a. i get to fix a low unit price per kwh/gallon³/subscription length. which means they cant do their 'variable rate' surprise changes several times a year, so i maximise my utility gain
b. i dont get bills each month, i dont have to worry about the daily grind to pay off the daily demands which is mental relief to know i owe no one and i dont get surprised price rises

other money spending planning benefits by:
a. by purchasing stable(long life) groceries at a monthly level i save time and money compared to daily ad-hoc grocery shopping, less car fuel and other benefits of bulk buying deals
b. instead of storing burn money in a crap interest account that does not beat inflation, i use certain gift cards for the daily stuff as the gift cards offer discounts and free items, which also add up to savings
c. i purchase my tourist plans (vacations) upfront year(s) before the dates of visit so that i get good deals, and yes sometimes i also use burn money the day(s) before to get those last minute cheap deals and just cancel the old ticket to get a refund on old ticket to gain on new ticket(or contact customer service to transfer tickets and get a discount refund)
d. even things like restaurants i can reserve tables and prepay to not worry about in the short term of the mundane daily grind
e. usually i find i still have some left over burn money which i just put back into bitcoin at the correction low, so it feels like i missed nothing

the whole long term planning has alleviated any old stresses i had decades ago in the old daily grind rat race game of fiat

i get more time, more produce, more services, better deals, mental freedom and not a slave to my home countries money..
..compared to relatives who use their domestic currency bank account card several times a day, i probably use my domestic currency bank account card maybe once a month

side note: bitcoin allowed me to retire young, i get to travel the world, experience different cultures and i dont think about my home countries currency as a daily threat, its something i dont feel even affects me or is part of my life. its not something i need to hold onto, im too busy enjoying life

Some people take Bitcoin in exchange for services or sometimes Goods.
Though in recent some don't care about it dodging third parties but how fast they can profit from it.

Anytime I hear about people favoring their local currencies for exchange.
I usually remember Gresham law that bad money (Fiat)  drives Good money from the market (Bitcoin, gold)
People would rather spend Fiat than save it.

physical banks will go out of fashion and just become app brands
most of the talk of CDBC is a central bank working with a dozen commercial bank brands to offer something easy like visa/..without banks paying/relying on visa/mastercard as a backbone payment system, thus bringing it inhouse to the banks and government shared CBDC network

visa/mastercard could go extinct