Let’s use this opportunity to talk about use-cases (or jobs to be done) in UX design. Here some designer figured people need two things on podcasts:
1. They just missed something and want to go back.
2. Current topic is boring so they want to skip forward.
The same designer probably thought that 10 sec is best for catching up something you just missed, and 30 sec is an average half-length of a topic to skip.
And she might not even be wrong! This might be a good guess. The mistake here is assuming that average (or most common) values are the most important values. In reality, MANY other situations exist, in which you might want to skip both backwards and ahead by 5, 10, 15, 20, 25, 30, 60, 120, 240, — any number of seconds, really.
That’s why nominating most common values is a mistake: you enable most common case, but at a price of sacrificing many less common but still valuable ones. What you should do instead is give users fine-grained control (e.g. symmetric +/-10 sec) and let them USE controls to adapt to the situation they have in hand. A car with a single “go to destination” button is infinitely less useful than a car with a steering wheel. The latter is less convenient most of the times, but it also has so much more uses.
Thanks @delaguardo for the picture.