How come most Near Field Monitors don't have (or even give you the option of adding) speaker grills?

Could the reason 'really be' that a grill would significantly compromise the quality of the speaker's sound, or are the manufacters just to cheap to add a protective grill?

I recently purchased a pair of KRK V4's
http://www.krksys.com/v3/vseries_v4.asp

and really pleased with the sound, but feel its exposed speakers (both tweeter & woofer) are an open invitation for potential damage, either by dust/dirt collecting on the sticky surface of the rubbery(?) material on the tweeter cone, or a stray object (or finger) accidently hitting & damaging either of the speakers.

Interested in hearing other people's thoughts and opinions on this. Thanks. - Scott