Hi Ksia,
The only reason I know of to not water the leaves would be the sun scorch but even then, I think if it is that hot, they will be dry again before any damage is done.
The only reason I don't water mine with the hose is that I seem to nourish the ground around them for (more!) weeds to grow. When I get the kids do the watering for me, they use the hose and no harm has ever come to them. :D
I am trying a new method with my toms this year by not watering them at all!
Apparently, if you give them enough space - about 2' either way, they get their roots deep down until they find water and don't need to be watered!
As a precaution though, I have planted upturned 2 litre bottles (with the bottoms cut off) next to each plant so I can give them an emergency boost if I think I am going to lose them!
Also, to save losing water to the atmosphere, you need to create a 'dust mulch' by doing lots of hoeing.
As I live in the South and am under threat of 'drought regulations', I thought it a good year to give this a try!
All the best,
Donna.