Your points are absolutely true! Bitcoin is a currency system which effectively eliminates the need of an intermediary and is not limited by international borders! Still we take it as an investment! But here we need to understand why!
Being a common people, how often do you really send international remittance? How often do you really make international purchases? How often do you face such situation where you can't use your bank account to send or receive funds? If you can answer these questions, your concern will also be answered!
Those who need to use bitcoin for anonymous and intermediary free international transactions, they are using it! But the number of such people is very less! Majority of the bitcoin users look at it as a method to make money, either by holding or by trading and there's nothing wrong about it!
Bitcoin is popular today because it has given financial freedom to many people. So if people are happy that way, let it be an investment and a reason to happiness!
yes you are right bitcoin does give us convenience in international transactions without limits but transactions like this are very rarely done. and maybe the main purpose of Satoshi to create bitcoin is not for investment tools but if in fact at this time bitcoin is used more for trading and investment than payment instruments we have to accept it. because by investing in bitcoin we can get a big profit.