I got tired of having different shims for different lenses, needing to position the shim (yeah, yeah, first-world problems :)), and working in the offset from surface for different thickness of material and cutting vs engraving.
Behold, the DRO!
If I get really squirrely, I can add a Z-axis motor and push-button zero/adjust…
It was a practical consideration. Less expensive and there wasn’t much clearance between the table and the frame. Plus, certainly don’t need the resolution of glass
