sweden - Why do Swedish postdoc ads typically have a requirement that PhD date must not be more than 5 years ago?

Ads for postdocs in Sweden appear to always have a rule like PhD degree obtained preferable not longer than three-five years ago:

Example 1, 2. I've seen it many times in the past but job opening links are particularly temporary.

Is this to protect people from becoming career postdocs? Is it a requirement from a funding agency? Or is it just a habit?