Can you spouse/partner/girlfriend/boyfriend be your best friend?

You see I have always heard about people saying that so and so my love and my best friend meaning their spouse or partner. And they are so fond and proud of saying it and it just makes me think, yeah sure why not? If you are going to call your spouse etc as a best friend then what are going to call your best friend then and do you really believe that you will do things with her/him the way that you do with your best friend? Would you share your financial information with your friend and would you sleep with your best friend (male or female) and would he attend to you if you are sick and stay with you the whole time in the hospital like your spouse etc does? (Maybe they will and maybe they would not). There are certain things that you share with your spouse etc and there are certain things you share with your friend. There is a reason a friend is a friend and not a spouse etc and vice versa. In my opinion, the word best friend and spouse cannot be used interchangeably since they are two different relations with two different set of priorities. Although you can have fun with your significant other but you cannot discuss your future plans and responsibilities with your friend and sometimes the things that you say to your friend or just spend time with them stress free, you sometimes cannot do that with your significant other. So at least me the euphoria about your significant other being your best friend is just that euphoria and your significant other cannot be a replacement for your best friend and vice versa.