Sometimes they are and sometimes they aren''t. Depends on which lab graded the diamond, the nature of the inclusions, size of the diamond, type of cut (a RB can easily be eye clean, an EC most likely not), and how eagle-eyed you are.
I think there are many but not all, AGS & GIA certified SI-1 Round Brilliant; Princess; Radiant, Cushion, Pear; Oval & Marquise shaped stone that are eye clean. The many facets help masked the inclusions. However; there are probably not many step cuts SI-1 that are eye clean.
I have a SI-1 and it is eye clean, and almost 10x loupe clean.