I think that 30° is the most pleasing and reassuring leg spread for a tripod. That way the legs form an equilateral triangle with the ground. A wider split might put too much sideways force on the feet and too much pull on the spreader. A narrower tripod is easier to tip over, especially with a top-heavy load of an EQ mount and telescope.
Since my HEQ5 tripod collapsed I've been on the lookout for a replacement, and the manufacturer of my new tripod gave me the option to customise the angle. So I chose 30°.
Thanks all who took a minute to measure their tripods
Cheers
Steffen.