Keyboards seem to be a perfectly understandable "thing" to wrap a hobby around. I use mine for hours, every day, and it is interacting with me, and specifically my fingers, more than any other physical object in the world, including the wife and my car's steering wheel.
There are people who surely have ten times the numbers of shoes that most of us have keyboards, and while they may be considered frivolous or wasteful, they are not looked upon as "weird" (in most cases, at least).
Collecting some things, such as coins or artwork, has some component of investment involved in addition to aesthetics, and other collections (eg my records and CDs) are for personal enjoyment, primarily, but almost everyone has some sort of collection of something.
I like to work with my hands, and so it is important to have a collection of good tools. Why do I have at least 2 dozen screwdrivers, my wife asks? Because using exactly the right tool makes any job go easier.
So why do I have a dozen keyboards in boxes in the basement, but this same one has been on my desk for nearly a year? Well, maybe I do have a bit of a problem .....