I have never ridden in a skirt, and I can honestly say that I don't think I ever will for two reasons. Firstly, no matter how much you tuck it in, there is always the risk that it will escape and get stuck in your chain, which is something that could be incredibly dangerous for you. Secondly, unless you're wearing shorts understand, you risk showing your underwear - which is something that I would really rather avoid whenever possible! And if you are wearing another layer underneath, then you might as well just wear that one and then not bother with the skirt at all. So no, I wouldn't wear skirts when riding a bike, as it doesn't feel like appropriate sportswear as far as I'm concerned.