I think part of the issue is that each reader has a different level of skill. Some get exact answers while others abilities are a bit more hazy. The latter type has to transfer these not-overly-detailed feelings into words, and so they may answer a bit more vaguely because they don't feel confident enough to make stronger statements.
Some people also believe that Spirit or whatever is involved and may block out or allow certain information to come through based on that person's life path. So in that sense it's possible that some psychics are being either fed information or being blocked from seeing certain information. If that's true, it would make sense that some might get related information, but not a solid answer to the exact question.
Perhaps some are bad communicators, they may think that they communicated what they saw but they really just made a generalized statement.
Another possibility is that sometimes the psychics actually see more than they say, and edit it out because they are afraid of being wrong or having the person get mad if it's bad news. At the end of the day, this is a business, and some may be afraid to say things that are too negative.
It's possible some don't have much or any abilities and are just dancing around anything that you could validate to tell if they are real or not.
I don't know, I have begun keeping a prediction log where I write down a brief overview of the predictions after the readings so I can then come back periodically to the log to record which were correct and which were not. It's hard because some psychics actually get the present energy right but are wrong in their predictions, and then some readers could be very vague in their delivery but their predictions could ultimately make sense or be more true later on.