The reader begins a book trying to place himself/herself in the space and time of the story. The reader hopefully wants to be in the story. The author wants that too.
She nearly killed an innocent man. (Gone, Kellerman)
So, the reader starts creating a world, with a female and an innocent male that she nearly killed.
But that was just a goofy first line, the author didn't really want to tell the story starting from that point. So the story backs up in time and switches characters.
Creighton "Charley" Bondurant drove carefully because his life depended on it. Latigo Canyon was mile after mile of neck-wrenching, hairpin twists.
So the reader is abruptly pulled out of one time and tossed into a new one (with a new character). The next paragraph again jumps backwards in time, to describe mostly setting.
That's another adjustment for the reader, though smaller than the first.
A few paragraphs later the story finally reaches the starting time of the scene:
This morning, he was...
The author could have, after that goofy first line, jumped all the way back to the morning. Perhaps feeling that jump was too large, the author chose to make several smaller jumps.
The goofy first line often disturbs micro-chronology, which I defined as the temporal order within a paragraph. Now we are talking about time on a broader scale, which I called macro-chronology. As already noted, the goofy line can substantially disturb macrochronology too.
But many if not most starts create some need for time jumping. Again, stories usually don't start with the first event on the timeline.
The Effort of Time Jumping
Time jumping uses the reader's effort. First, it takes time and effort to relocate. Once relocated, it takes the reader time and effort to become re-absorbed into the story. And moving into the past for a flashback means two relocations – one going back to the past, and one returning to the present.
Second, the jumps are usually marked, which takes time and effort. Yes, perhaps not a lot. But at least some. The book I am reading now begins the second section "1985". A jump forward? Presumably How far? I had to search for the heading for the first section to know.
The first jump in the example above is marked with only an extra space between lines. That jump becomes obvious only when the reader notices that the story doesn't make any sense. The rest are marked verbally.
Two Ways of Presenting the Past
Sometimes past events are revealed through quick snatches of memory and dialogue.
"I remember seeing you on a sonogram for the first time. I was so happy I cried."
I remember being little – when grandma and grandpa came, I would dash to the door and always be there first.
"You remember about us goin’ into Murray and Ready’s, and they give us work cards and bus tickets?” (Of Mice and Men, Steinbeck)
Then the scene clock doesn't stop; then the reader doesn't have to relocate in space and time.
The other way to present past events is to jump back into the past. For example, a flashback. This does ask the reader to relocate in time. (Sometimes the memory of an event is so lengthy it becomes a flashback.)
Time jumping uses the reader's effort, as already explained, I hope. Moving into the past for a flashback means two relocations – one going back to the past, and one returning to the present. So that's one problem of putting events in the past.