I've got a number of tattoos, as does my wife, so I'm naturally inclined to disagree with you (and of course, I also disagree with you due to the fact that you're simply stating your opinion and passing it off as fact).
However, I will concede that some tattoos will look bad when people get older, however, not purely because the person is older. For example, a friend of mine has a large skull design tattooed across her chest. It's colourful and extensive and she has many others. I think that chest tattoo won't age well, but only because I don't particularly like it already. I'm not about to sit and pass judgement on it and say "in years to come there are going to be a lot of women in these age groups with terrible looking, and in some cases extensive, tattoos", because I'm not a judgemental p***k, but my personal opinion (which is by no means definitive) is that that particular tattoo doesn't look very nice and by extension won't look nice (in my opinion) in years to come.
That's not to say that all tattoos will age badly or on all people. As to why you've singled out women I have no idea. I would suggest that you're simply a bitter sexist. I accept that you're older, but sexism, like any prejudice, can't simply be explained away by stating "it's a generational thing". To have to state that you "try hard not to be sexist" says it all really.