I've been rewatching early seasons and I've noticed something.

Allison would rarely actually see the crime getting committed, let alone the perpetrator's face. 

For example 1x3 "A Couple of Choices". She didn't see the killer, but felt (didn't see, felt) that there had been three people at each crime scene (four in the case when one victim was pregnant) at the time of their deaths, meaning that it couldn't have been murder/suicide. When they found the killer's place and the other couple was soon to be murdered, one of the victims (Lee's sister-in-law) told her what couple the guy has set out to kill next.


2x2 "The Song Remains The Same". She kept hearing that song in her head, that led her to an abduction sight. She heard the same song while shaking a hand with a priest, and concluded that he is somehow involved. Then she started having those dreams about a plane crash killing her family, making her to decide (and convince the rest of her family) to go to Joe's sister's wedding by car instead of by plane. The crash didn't happen, but by choosing to drive to there by car they found Isabel and rescued her.

In later seasons, she would have several separate dreams showing, often pretty straightforward, the events leading up to the murder, up until the final dream that would reveal the actual killer, or at least some event from the past that would make her tie everything together.

I actually preferred it the way in early seasons. It made everything more realistic (if you can say that about the TV show featuring a psychic) and made Allison more relatable since she had to put more pieces together herself, despite her abilities. And her psychic abilities weren't limited to only two senses.

I mean, if the victims/universe/God keep sending her those messages, why not reveal the whole thing right away? More time before the killer is caught=more time for the killer to flee, dispose of the evidence, murder another victim.