Leaving is easy. Why stay?

There are some characters you need in your story.

Sometimes you need an ex to still be around. Sometimes your protagonist needs a high school friend that never abandons them. Sometimes a childhood crush has to be the solution to a self-esteem issue.

The problem is: there isn't always a reason for these people to still be around in your protagonist's life.

The world is huge. There are opportunities everywhere. Your protagonist is not the main character in everyone's life.

Why would the people who can most help shape your story still be around when inciting events are happening to your protagonist?

There can be a lot of reasons, but you have to make sure you pick one. If someone from a long time ago is still in your character's life, you may need to justify it. Find the right reason for your story.