Well, that's one more thing Kosara and I disagree about.
Standard datasets _are_ important. You literally don't want to be surprised by the dataset when you're trying to understand a technique.
Synthetic examples serve a similar purpose: you _know_ what's in them, so you can check that your technique is doing what you expect.
If you design a new technique and show it on a new dataset, readers can't separate one from the other.