This is a question I used to get a lot, because there usually is a perfectly good reason. Except when there isn’t.
Why do you hang tee-shirts upside down to dry? Because tees are made of knit fabric. Knit fabric is not fixed in width or length, but flexible and stretchy (woven fabric is only slightly stretchy, primarily on the bias.) When it stretches lengthwise, knit fabric gets narrower widthwise, and vice-versa.
By hanging the tee shirt upside down the fabric near the waist is getting the most stretching (because it is carrying the weight of the rest of the shirt), and that will reduce the tendency of shirt waists to get stretched too wide (and also keep the shirt a bit longer, reducing ‘plumber butt crack’.) Doing it the other way, with clips holding the shirt at the ends of the shoulders, will also cause the most stretching to happen there – and you may look like you have little horns at the tips of your shoulders.
So, three reasons to hang the tee upside down to dry: avoid antlered shoulders, and stretch the garment the right direction/the right place to reduce too-wide-waist and butt crack exposure.