To be fair, magical girl shows for kids in Japan are huge franchises with theatrical movies, boatload amounts of merchandises, live action theatrical shows, video games, and even food products.

In Japanese magical girl shows you get the same issue in reverse: they're very careful to make the show as girly as possible with very few male characters (often none at all), because once again advertisers want a segmented audience. E.g. after Heartcatch Pretty Cure took a more serious tone and acquired a periphery demographic the next two series were made deliberately more girly and lost the dramatic arcs.

I always thought the target demographic for magical girl shows were the so-called "grass eater" or herbivore men. There's a reason why Akihabara is very popular, and I'd imagine most of the toy sales come from adult men rather than girls.