That's exacly why I use it too. As a simple profylactic measure. It stops you from accidentally touching the front of the lens and such. These days the coatings on most lenses are good enough to eliminate flare in all but the most difficult lighting conditions, but the hood will still protect the front element very well.
my lenshood is always on, day or night, outdoor or studio, the only time I take out is when the hood is getting in the way if I shooting in a tight confine space or with some filters, or I keep my camera into the bag.
Worst case.. no effect on pictures (unless you used the telephoto lens hood on the wide lens, or is trying some special flare effects). Other cases, possible improvement to picture quality by reducing undesirable effects like flare.
I look at it this way, besides taking up space in your bag, there is bascially nothing detrimental a hood can do you your pictures; unless of course you have an incompatible hood, then you might get vignetting.
the hood might block ur built-in-flash when it fires. the result may be shadows appearing on the bottom of ur picture, especially if u are shooting at the widest end. i am not sure if that will be the case for ur 18-55, since it is quite small.
An example from a victim on flickr. (from member neildettwiler)
as a general rule, use it when needed. just dump in ur camera bag. use it as and when u see fit.
I dun even bring my hoods out of my Hoods Cabinet. The only time i use them
was when they are inbuilt like my 16mm FE ...
Not overuling the importance of them, they can improve contrast and many other
advantages outlined as above, but for me the use of filters can be pretty inconvenient.
Usually i will just improvise with my hands ..