One of the problems is that what we call 3D printing actually isn't. It is actually 2.5D!
The reason is that whilst the print head/LED moves/scans continuously in the X & Y axes, the Z axis [vertical bed movement] is a finite step. What is currently under development is a continually moving bed for SLA printers. That doesn't exist yet but there is an interim halfway house [a sort of 2.6D printer] where the print bed rotates and that, in my experience, quite dramatically removes the stratification on models with spherical surfaces.
I've just had the 7mm Bedford RL cab printed on a Stratasys J55 agency printer and for a vehicle cab with multiple curved surfaces, there was almost no cleaning up of stratification to do.
These are very expensive machines and because of their being a 'work in progress', available only to commercial agencies. However, the quality of agency output continually improves and the true 3D SLA printer is (I am told) in sight.