Does anyone know why Burris doesn't make their Signature rings (the ones with inserts) in LOW?

Probably because these rings allow a hi-mag scope to be pointed up (more closely to parallel with the bore) enough to shoot at closer targets. Hi-mag scopes usually have a big bell out front. I have a 30mm, 10-40X that uses the high rings. I have the tens in it, and it's still not pointed up enough for me to hit anything at less than 300 yards. I was elated when I saw the twenties are available, then my heart sank when I saw that they were only to be had for one-inch scopes. Bummer...