Personally, I think homeopathy is ridiculous and I'd never use it, but I ask the question because homeopathic medicines are not the only drugs which doctors prescribe which only have a placebo effect.
Compare homeopathic medicines with anti-depressants. Homeopathic remedies will not cure you, but they are not toxic either, unlike anti-depressants, which can have unpleasant or harmful side-effects. In 2006 UK doctors issued 31 million prescriptions for anti-depressants, and 38 million in 2008, even after a meta-analysis study had showed that anti-depressants are no more effective than placebos, except in the most severe cases of depression (and even then the difference is "relatively small"). Is the number of prescriptions still rising?
Arguably, depression is a special case. If the patient's mood is lifted, does it really matter whether the effect is placebo or not? I'd argue that it does matter because of the drug's harmful side-effects; it would be better for GPs to prescribe a real placebo, that is something which has no effect at all -- like a homeopathic remedy perhaps?