You are right the reason people invest in Bitcoin is so they can make profit from it later in the future if not for the profit no one will be investing in it because people invest only on something they know they can get profit from but Bitcoin is not only used for investment purposes just like you said Bitcoin is also used for transactions some countries has declared Bitcoin as a Legal tender and when you go to the mall or supermarket you can pay with Bitcoin after buying things,
Bitcoin was not created to be an investment, Satoshi never mentioned that when he created Bitcoin. We are the ones who turned and used bitcoin as a profitable investment instead of using it for its original purpose but I agree that: if bitcoin was only used as a currency and did not increase in price, perhaps not many people would need it and it would not be as popular as it is now.
So far, El Salvador is the only country that considers bitcoin a legal currency.
the reason why other countries have not adopted this is because they feel Bitcoin is working against there economy some countries has fought Bitcoin but is impossible to remove Bitcoin because Bitcoin has no CEO and is a decentralized coin since the government can't control the finance of people like they do in Banks they are not happy Bitcoin gives you the opportunity to control your own money and your money is more save in Bitcoin than in bank no matter the the situation your money is always save in Bitcoin and this is one reason some set of people invest in Bitcoin so is not entirely for profit making there are many reasons people invest in Bitcoin but mostly is for profit making.
Simply put, government is a centralized system and that gives them power while bitcoin is a decentralized system. The government's power would be somewhat threatened if people switched to bitcoin, so it's understandable why they are not friendly to bitcoin or don't want to legalize it.