15 minutes is nothing if your watching TV, or scrolling aimlessly through your phone.
But a 15 minute delay on your train is annoying and frustrating. If your friend is 15 minutes late it’s fairly annoying.
But 15 minutes is enough to get quite a lot done, it’s enough to get a stretching routine done, it’s enough to write a blog post, read a good amount of a book.
It’s all 15 minutes it just depends how you look at it and how you use it.