Some occupations are male-dominated, and some are female-dominated. The fact that some occupations are male-dominated tends to give rise to worries about discrimination, overt or covert, present or past. The fact that some occupations are female-dominated tends to give rise to fewer such worries, though it may give rise to some. But as far as I know, very few people worry about the fact that some hobbies are male-dominated and some hobbies are female-dominated.
If the reason we worry about male-domination in an occupation is that we are concerned that women miss out on opportunities for living a particular meaningful form of life, then we should be equally worried in the case of male- and female-dominated hobbies. After all, for most people in the world, one's occupation is primarily of instrumental value—any other occupation of no greater irksomeness and no lesser earning potential would be just as good. But hobbies are of non-instrumental value—they directly give value to life. So if the worry is that the individual woman loses out by being discouraged by society from taking up a particular occupation, we should also worry about the individual woman or man losing out by being discouraged by society from taking up a particular hobby.
A different reason to worry about male-domination in an occupation, however, is that society loses out by this domination, either by losing out on the distinctive contributions of women, or by losing out on almost half of potentially qualified candidates. This worry, however, I think is only going to be very strong in the case of those professions that both provide significant social benefit, and where the benefit provided depends, in existence, kind and/or degree, to a large extent on the individuality of the worker, or in cases where there is a shortage of workers. Thus, mass-production of buses provides a significant social benefit, but the benefit does not significantly depend on the individuality of the line worker—any other line worker who does his or her job decently would do just as well—and as far as I know there is no significant shortage of autoworkers. On the other hand, the writing of novels or the provision of medical care provides a significant social benefit, where the existence, kind and degree of benefit all depend strongly on the individuality of the worker.
Insofar as it is these kinds of social contribution things that worry us, we are not so much concerned about the injustice to the particular woman kept out of an occupation, but the loss to society of her distinctive potential contribution. And this kind of worry does not occur in the case of a hobby, since hobbies, with some notable exceptions (e.g., the production of open source software, or the writing of poetry—both of which could just as much be occupations as hobbies), tend not to be of great social benefit, important though they are to the individuals.
I suspect in practice we have both kinds of worries about male-domination, to different degrees in different cases.
