Cover your eyes in addition to your mouth and nose; they also cover your face so stop the prospect of a respiratory droplet landing on your face which is then (for want of a better word) smeared into contact with a mucous membrane.
Make it much harder for you to touch your face (a bit like a dog collar for humans…!).
 Offer the potential for decontamination and reuse (although disposable is probably ideal).
Have less chance of prompting the occupational hazards of long-term wearing face masks (painful / damaged ears and nose bridges).