I don't think I agree. Or, rather, while it might be that most interests and ideas are actually only indulged in by a minority, there are some that get so much media recognition that they appear to be "mainstream", while others - which might, if you delved into it, be indulged in by just as many people - are labelled "minority." There's a perception of mainsteam culture, anyway. Compare the media coverage given to football, compared with computer gaming, for example. Or the coverage given to soap operas as opposed to television history programmes.