Plus, 'suckers' generally do not contribute much (if any) to thickening the nebari...or 'gaining mass' of the trunk, so to speak. Suckers just suck the 'energy' away from what was formerly the 'leader'; suckers tend to be more vigorous than old leader so tree is no long 'balanced' of growth-energy.
I use terms pretty loosely there, but I bet you see the picture of how suckers can dominate efforts to maintain one trunk or such
Rarely are suckers useful for bonsai 'planning/development', per se.
I have always been of the opinion that suckers originate off of 'roots', or from root/above-ground tissue interface (forget 'real' name), or even from roots far from trunk like in numerous oaks. If its a branch off of the trunk (proper), not a sucker (right?) UNLESS the branch is below a graft
, then its a sucker
no matter the angle you look at it
If I remember right, most suckers are poor transplant 'candidates' as they usually root poorly - they do grow fast, but can't make roots worth a darn, IME.