Your story's ending is the final determination of whether the reader will go on to read more of your books or move on to another writer. The more compelling your ending, the more likely the reader will buy your next book.
The middle of a story can be one of the hardest parts to write. It can be challenging to keep the middle interesting enough for your readers to finish the story as it begins to drag into predictability and they start wishing it would get to the end already. To combat this, we need to give our midpoint as much importance as we do the other plot points.
Beginnings need to cover a lot of material in a short space of time. But we don't want to slow the story to the point of the readers losing interest. The readers want a story, not background noise. And a slow beginning is a lot easier to walk away from, than later when the reader's already read half the book or more.
The opinion among writers today is the prologue is unnecessary and detracts from the story. But that doesn't mean the prologue has gone extinct. It still serves a purpose when used correctly.