To some listeners, that may be true but what about the artists? I'd argue that most artists have more eclectic tastes than what their music suggests. So what is stopping them from putting all kinds of stuff on their records? Whether it is the "industry", their fans, their own insecurities, the want to make a "cohesive" statement, whatever, most (=practically all) artists are clearly working within boundaries that, more often than not, fit genre conventions...