I think real psychics will not hold back and if they see something negative they will tell you. I think that most psychics on those hotlines are not real and therefore what they are good at is telling you a story. So I think some of them tell you a positive story and some can tell you a negative story. They put enough details that you can't verify so that it makes you feel like they know what they are talking about. Each of those fake psychics has their own way of telling a story so some might enjoy saying something positive and some might really enjoy saying something negative.
I don't think because if it's a negative reading, then it must be accurate. Nope, I had negative readings that were far less accurate than positive ones.
So I think the main thing is to identify the fake psychics who tell stories and are very good at making up a believable story, actually I think this is a skill that can be cultivated and perfected. I've been told this by people who know psychics who work for hotlines who openly admitted that they are actors telling stories and it's all fake.