BASS or BASS? why oh why?

Because English is really a creole language--a mixture of different languages: Latin, Greek, Gaelic, Celtic, Pictish, Anglo Saxon, Cornish, Welsh, French, Old Norse, and many others. Many of these old languages changed over time; sometimes the spelling changed, sometimes not. Also, the spelling of English was not standardized for centuries, education before the 19th century was often sketchy or not available for many people, and so people spelled pretty much as they heard things. Eventually, people decided there was a need to standardize and simplify spelling, and this was the beginning of modern spelling.

This is a very simplistic answer--the following links will give you better information.

This was an interesting question--I'm glad you asked!