Leveling A Mill: Why?

[4GSR]

My mill is setting on four blocks of 1 x 6 wood. When I place my carpenters level on the table, it shows level in both directions. Good enough for the girls I play with.

Now my lathe, that's another story...

 

[rick9345]

My eyeballs like the the level to the earth look. Otherwise square to the spindle is more important, and coolant drain consideration.