Having the reponsibility of serving ranking officials their daily meals, my dad used to be part of a crew tasked to prepare lunch and dinner with top notch class similar to a 5-star hotel.

It's excusable if there was something accidentally spilt or dropped on the floor that needs immediate attention.  But more often than not, crew members clean the floor as part of their daily tasks without being considerate to the diners.   The chemicals sprayed used in cleaning alone is not sanitary as particles of the spray coming out of the nozzle may float in the air and contaminate any food currently nearby.  I certainly wouldn't want liquid soap particles floating around my meal.

In addition, you know the feeling when you're eating and then someone tells youa gruesome or disgusting story ?  It's enough to immediately stop eating and lose your appetite.  Well a crew member mopping a floor can have the same effect.   It's not visually appealing seeing a floor being mopped especially while you're chewing something and much worse is if you see the dirt being collected.   Some people may have stronger stomachs and can ignore this.  But I'd say it would be best to cater to all in being considerate.

The cleaning should be done when there are no customers.  Other establishments close an entire section even if only to clean a certain portion.  I'd say this is more acceptable than a crew member mopping away passing through diners left and right.  I even had some crew disturb me while I was eating  and ask to put my feet up so he could mop the floor beneath me.   I call that inconsiderate even if he was just doing his job.

I wish food outlets be sensitive and aware to this.  I have the notion that as long as they see crew members cleaning up the place, is that sanitation is at an all-time high. There's a time to eat and a time to clean.    And they don't go good together.