I'm not sure how it "turns off fans," since most ignore them or have never heard of them.
Many of the ranking services have remarkable records of getting the rankings correct, and many times they end up being "wrong" is due, at least in part, by injuries. Sure, there have been huge misses not just by services, but by all teams' evaluation systems- see missed draft picks, mistakes made on prospects, left and right.
Many fans are drawn to paying attention to the farm and its players. They like to know what non-team biased people think about those players. Those who don't want to know, can and mostly do ignore it all, until the kid is raking it in MLB or flopping.
To each his own.