The violin seems to demand good posture. Your right arm moves from the shoulder a lot as you shift the bow from string to string, and your right elbow has to be out a bit for that to work. The fiddle is tucked under your chin on the left side, and if you're not standing up straight it slides down towards the floor. Your left elbow needs to come forward a little bit if your left hand position is going to comfortable.
All of this means you really have to (or, at least, I really have to) stand up straight. That in turn means that the sheet music I'm reading from needs to be easy to see when my head is up and my eyes are looking forward and to the left. If the music is on a desk, I have to bend over to see it, and my posture falls apart. The elbows drop, the head turns and the fiddle slips down my chest. Balancing the sheet music on my knee is even worse.
None of that happens when you use a music stand. First of all, a music stand is adjustable. You can make it as high as you need, and you can move it around easily so that its position relative to where you're standing or sitting is comfortable. Also, it holds the sheet music vertically, rather than horizontally as it would be on a desk, and that makes it easier to read. And good music stand is solid enough that it makes a useful writing surface.
I have heard that the word “genius” started as the name for a spirit that lived in the walls of an artisan's workshop. The genius would come out of the walls and help the artisan work. In this version of the world, you are not a genius – you have a genius. I like this idea a lot; it shows the importance of designing and equipping your work area in a way that supports the work you do. Good lighting, a place for your tools, enough room to work, sound or silence as you need – it all leads to better work. That's what the music stand does for me as a beginning violinist. It's an element of my work space that makes me work better.
There's one more thing I like about a music stand, although this one is a little fuzzy. The stand is a solid, real-world, daily reminder that there is a way to define yourself that includes being a musician. For the most part, only musicians use music stands – so why have one if you're not a musician? There's really no other good reason to have it.
It's a tool for the hard work – practicing and playing. You can read about the great composers without a music stand. You can learn theory without a music stand. You can write music, write about music, listen to music, all without a music stand. The stand is for when you actually want to be able to do thing thing that sets musicians apart – play music.
You may get a buzz from owning an instrument, especially if it's rare, expensive, beautiful, unusual, customized to your needs, or great-sounding. You can get that buzz whether you play well or not, or even if you don't play at all. The only buzz you're likely to get from a music stand is the one that says, “I could be good at this.”