You say that as if that's the only thing that could be a determining factor in the subject of question.
The lack of interest is what experts currently believe to be the cause. What other logical causes could you suggest? That fewer women are able to do this kind of work? This isn't true. Or would you rather say that they're somehow dissuaded from going into the tech field? This isn't true either.
There are many organizations out there that try to get girls interested in technology careers. I volunteered for one of them. Just saying. :)