Actually it did exist and was an alternative to the mainstream audio magazines of the day. When JG Holt established "The Stereophile" in the early 60's it was to describe the subjective sonic characteristics of audio components, a first of its kind. It was a different approach in that the magazine didn't accept any advertisements unlike the other audio magazines of the day. There was a problem, it relied totally on a subscription base with no advertising. Of course from a business model perspective it meant that folks would have to pay more than the other magazines that accepted advertising. The value to the reader that the information provided would be ideally unbiased and uncumbered by the pressure from advertisers. It would provide what the reviewer heard (JG Holt) as well as measurements and how the two might correlate. The problem is the over the years, the magazine was never published on a timely basis which gave rise to another publication in the early 70's, The Absolute Sound with the same idea but a more timely publishing schedule.
Both of these magazines have evolved over the years and in order to stay viable and become profitable (a novel idea wouldn't you say?) decided to accept advertisements. It is tempting to be cynical when there is a conflict at play namely, is the magazine always being totally objective in describing subjective preferences and differences in components? I feel for the most part they do. Are they pressured by manufacturers' for good reviews of their products with the risk of losing advertising if not positive? I suspect that happens too. It isn't a perfect world and maintaing a viable business in a constantly changing business environment is not always easy. While there has been an evolution of both of these magazines most particularly Stereophile when Larry Archibald sold it to a larger publishing concern, I'm sure other pressures on the Editor/Publisher came into play. We as readers can't know these details but we can only rely on our own senses and experience when reading reviews.
There are numerous e magazines to read and there is a wealth of information, more than ever before, for audiophiles to gather data in order to make sound purchasing decisions. But yes, I agree, virtually any consumer interest magazine that accepts advertising yet reviews products can be viewed as nothing more than entertainment and "pretty pictures".