Some minor spoilers for Spider-Man: Homecoming can be found throughout this article. Read on if you don't mind hearing 'em.
There are a lot of differences between Marvel's Peter Parker and the big screen incarnations of Peter Parker we've seen in the past. One of the most noticeable differences was probably Peter Parker still coming to terms with his new abilities, including climbing high into the air, this time around. While Spider-Man is usually a character who is totally comfortable with leaping off of skyscrapers, monuments and more, this version of Peter Parker got nervous while scaling the Washington Monument. Screenwriter Jonathan Goldstein recently revealed that dealing with fears was a major part of showing this version of the character's story. He said:
We wanted the movie to focus on him coming to terms with his new abilities and not yet being good with them, and carrying with him some real human fears and weaknesses, like a fear of heights, because nobody ever dealt with that before. You just sort of assumed, 'He gets bitten by a spider, he's totally comfortable on top of tall buildings,' but why did that have to be the case?
Personally, I thought Peter Parker not being certain of his abilities was one of the more intriguing facets of his personality this time around, as it raised the suspense and gave him room to grow. Although most Marvel fans know Peter Parker is going to be back for Avengers: Infinity War, the stakes still felt a whole lot higher when Peter himself was unsure of what he could do with his body, not to mention what technology he had at his disposal. We felt Peter's personal terror when he was standing very precariously near the top of the Washington Monument and realized he has to push himself off of it in order to get through the window. We also felt his terror when he was buried under rubble thanks to the machinations of The Vulture.
Speaking of the latter scene, other script writer John Francis Daley also told THR that all of these scenes were created so that we could see Peter Parker change and grow up in a lot of ways. He needed to "accept himself" before he could go out and save the world. And all that culminated in the rubble scene.
We have him starting the scene with such self-doubt and helplessness, in a way that you really see the kid. You feel for him. He's screaming for help, because he doesn't think he can do it, and then in the context of that flashback, he kind of realizes that that's been his biggest problem. He didn't have the confidence in himself to get himself out of there.