I think you are asking if one should leave the dust cover on during play or not. I have owned a MMF 7 in the past and never liked the sound with the dust cover on, flipped up or not. The MMF 7 had hinges that allowed for easy lift off of the dust cover. I'd remove it while the table was in use and replace it when I was done.
IMO, it is not a must have for maximum vinyl enjoyment. However, as others have posted there are many excellent reasons to have one. Currently I have no issues with hands of any kind and I haven't had a dust cover for several years. I do carefully use swiffers and microfiber cloths pretty regularly.