Most, heck, nearly all, do not. This is why suspension set ups have been looked at like voodoo for so long. Most of what most people do is a simple guess or based on what someone else has that seems to work.

Ideally I like to, but I can't always get things on a four wheel scale with any regularity. I'll at least do a front/back check at the local drywall place since they have a scale. To me, that is the minimum starting point to understand where your at and where you need to go.

Redistributing weight and lightening things up are always nice and desireable goals, but you can make a seemingly heavy pig perform well if you know your starting point.