Lapping in valves

As long as the seats and valve faces are not pitted, there's not a thing in the world wrong with a basic lap valve job. All you need to end up with is a good SOLID grey line all the way around the seat and valve face, with no breaks in the grey. As long as the seats and valve faces are in good enough shape to do that, you are fine. I actually prefer lapping over grinding or cutting, because you end up with much less metal removed and the valve stem heights are hardly changed. Just less machine work all the way around. How can that be a bad thing?