Always gone by the rule of "unless you actually do a job that legitimately gets you *dirty*, you don't need a shower every day". Unless you do construction, work outside all day, work in a hospital/germy type job, yadayadayada.
Plus, over washing and such can irritate skin, which will exacerbate skin conditions and potentially cause minor infections, cause overproduction of oil on skin/hair/etc. Actually not good for you, in the long run.
I try to go every other day. And wash my hair only a couple times a week (it gets oily otherwise). And tend to take baths as opposed to showers (didn't grow up with a shower, it is still odd and a bit foreign to me, honestly).