Why do English speakers sometimes use present tense when they talk about the past?

When you learned English in school, you were taught to use the past tense when talking about things that happened in the past. For example:

I got a text message from my sister.

But sometimes English speakers use present tense when they're talking about the past. Here's an example:

Something funny happened to me last week. I was sitting in a coffee shop. I'd been waiting there for my sister for 30 minutes. Then I get a text message from her saying "Where are you!?"

Why do they do that? It's a style of storytelling. If you're stating the events in an unemotional, factual way, you should use past tense:

Something funny happened to me last week. I was sitting in a coffee shop. I'd been waiting there for my sister for 30 minutes. Then I got a text message from her saying "Where are you!?"

But when people tell stories, they usually try to entertain the listener. They try to put the listener into the story. One way to do this is to use present tense instead of past tense.

Usually you start a story in past tense and then switch to present tense when it starts to get interesting:

Did you hear what happened to me this morning? So I drove to work, parked my car as usual, walked into the building. And then about 5 minutes later I'm in my office and I hear an announcement over the intercom, "Would the owner of a black Honda Civic, license plate blah blah blah, please report to the back parking lot?" And I'm like, "Wait a minute - that's me!" I walk out there, and...

The speaker will switch back to past tense whenever the emotional and exciting part of the story ends:

"...so I had to call a tow truck to come pick my car up and take it to a mechanic."

This mostly happens in spoken English, but you can also find it sometimes in literature.