Random observation

I was just thinking the other day- what is the big deal about alphabetical order? Yes, I know that it makes a handy-dandy filing system, but what I don't get is why the alphabet needs to be in a particular order in the first place. This isn't a unique thing- every alphabet has a special order, but there honestly isn't much of a reason for this. Sure, when you're in kindergarten the order (and the song that goes with it) makes an effective mnemonic device, but once you know what the letters mean, the whole thing feels arbitrary to me. The letters exist primarily as symbols for one or more sounds, and have no real qualitative value. In other words, A is no greater than B, and there's no concrete universal law that states that Z must be last (the ABC song must be different in Britain, where they say "zed"). This isn't a pet peeve or anything- it's just something I've been wondering about. If you can think of a compelling reason why the alphabet should have the order we all know (from a causation standpoint- I know the effect that alphabetical order has on modes of classification), I'm all ears.