Although it was originally intended to be cash it actually now is used as a "store of wealth" It allows people to build up wealth and be able to preserve it from government intervention and inflation. If you have stocks the ownerhsip and registration is controlled by a government and can be taken at any time from you.

Look at china where if you have a large company and take a stand against the government all your equity will be wiped out and you will be either imprisoned or banished to another country.

Cash in a government bank account is the same way, you can wake up one day and all your assets will be seized, your credit cards will stop working.

Bitcoin works because you can technically have your wealth memorized. You can memorize a string of charcters that allow you to bring money with you no matter where you go. NO government or other human can steal it from you (except through torture) but you can also easily not memorize it and instead distribute the keys throughout the world in opposing countries meaning even if you are attacked by one country you still have some wealth kept in another.

A store of wealth is what bitcion allows. True freedom from governments stealing your money because you have ideas which they do not agree with.

This in my mind is the main usage of bitcoin.

Other coins like stablecoins, or the btc lightning network have high value because they make transactions much cheaper as traditional banking systems are complex, error prone, and costly.

This is not a common man's dream, but one of privilege and wealthy background. The oppressed masses don't need Bitcoin, they have no wealth to "memorize" and jetset around the world.