what is so nice is if your best friend is someone you came across completely by chance as I did, hit it off really unexpectedly, and are still here for each other, years later. We don't meet, we don't live in each other's pockets, we don't even live in the same country now - but we are solidly there for each other, any time either of us needs us.
I don't have anyone I see everyday (apart from OH and work), I would find that claustrophobic - but I do have a few good friends now, probably for the first time in my life. We celebrate together and lend each other shoulders to cry on when needed. The best friend isn't part of that group but could easily be. Moral support is hugely important - you can have acquaintances by the shedload, but the person you contact in your highs and lows is a true friend.