That was light.
In the 60's and 70's a high percentage of signed acts used Sunn. Notably Hendrix, Mountain, Beach Boys, The Who, Geddy Lee, on and on, most of them documented in this topic.
The biggest problem with current bands not using Sunn is that there is no Sunn. You would be hard pressed to find a major artist without an endorsement deal.
You can't grant endorsements if you don't exist.
Also, I think the old Sunn amps are too hi-fi for the tone tastes of most modern bands. If you do see a Sunn in use it's usually a bass player, hi-fi is good in the bass world, not as desireable in the guitar ranks.
When you crank an old Sunn into distortion, in ain't sweet by anyone's tone barometer, they flat roar. This coupled with the facts that they are LOUD amps, and they are relatively inexpensive, probably explains their popularity with stoner/doom afficianados.
There is a signed band called "The Lost Patrol" out of NY who's guitarist, I think his name is Steven, probably plays a Sceptre rig. Lots of tremelo and reverb, very clean, almost Dick Dale-ish tone. Plays a couple of very nice old Mosrite Venture guitars. Very cool stuff, excellent tone. Definately un-doom. I say probably because he almost bought my Sceptre and in fact said he did buy one locally so he probably uses one.