There are reasons to bathe rats. Bucks produce a rather nasty oil that is not an aid to their health in most cases, which can cause smell, nasty appearence, and in the case of my boy Malakai, actually CAUSED skin irritation as opposed to help relieve it.
Also, my past boy crew (not my currents, as they are still not comfortable with people they don't know) did a lot of traveling and educational work, going out with me all over the place, and teaching kids and even adults that rats were loving, smart creatures deserving of a good life - This works MUCH better when they have a 'cute' as in fluffy, soft, clean, and good-smelling appearence. Though personally I don't care how they look or smell, when going out to local parks or to schools, it helps a ton when they don't look like the sewer rats people expect to see.
However, most people probably wont find any use in bathing girl rats - I found that as soon as one of my girls got a bath, upon return to the cage as a nice clean member of society, they tend to get pinned and peed on
For that reason, my girls normally only had baths before surgeries and vet trips, and dorum flea season.
(DISCLAIMER - I see this coming. If you're about to rant about me dragging my rats around in public and causing them stress, PLEASE take this in to consideration - they are in NO way similar to hamsters, I've owned both. Rats in my opinion have almost identicle personalities to small dogs, and when properly trained, enjoy being outside and meeting people, and being pet and talked to and fed treats by strangers. When out in public, I take every precaution to keep my rats safe. They don't go to pet stores or places where they may contract a virus from other animals, are not let to run on the ground outside unless it is in my yard, and remain on a leaash (YES, they are trained - they do not struggle on the leash and accept it, while being well secured) at all times when out of my house, unless they are in a transport carrier or on a vets table. Though it is never possible to be completly safe, as there are no vaccinations for rats, I take ever possible step to keep them safe when out of the comfort of my house. I have never had a rat get sick, hurt, or put in a jepardizing situation outside of my house, and never subjected oen of my rats to something that was extremly stressful or hazordous to them... Besides the vets office
)
Er.... I apologise for another uber-long post. I can't keep my words in my mouth
But, yeah... With the hamster thing, I totally agreed
Never bathed my hamsters, even when I was a youngin', never needed to.