Be rid of Allergies: or at least drastically reduce them. Dust, dust mites, pollen can cause flu like symptoms, which make you less productive and make life a little miserable. Get rid of allergies, and asthma or respiratory issues with regular cleaning.
Be rid of Heath risks: sanitation gets rid of foodborne illnesses, like E. coli, staph or salmonella. These are bad enough for healthy adults, for infants they can be fatal. There are also substantiated links between bathroom hygiene (ie: a clean toothbrush) and cardiovascular health. Don’t risk serious infections or long term stain; keep things clean.
Increase safety: cluttered walkways and unorganised possessions increase the risk of injuries. A dirty floor is easier to slip on.
Do away with pests: Insects and even rodents will move into an untidy residence. A clean home will prevent this, and prevent the need of chemical deterrents. Maximise the insect resistance by using plants that naturally discourage pests.
Improve a Mental State: Not to be underestimated. There is such a thing as creative chaos, but anything more than a little chaos quickly becomes overwhelming and unproductive. A clean slate provides space for open thinking. There are a million ways to use neat and open space.
Encourages activity: A messy kitchen won’t encourage you to cook; you can’t even start cooking till you’ve started tidying up. The same goes for the whole house. No mess means you can get a clean start to whatever you are doing.