What is Krausening?
Commercial brewers and homebrewers alike employ experimental and traditional brewing techniques to get their craft beer just right. One of those techniques is Krausening, a traditional German approach that eschews adding any sugars or extras to the fermented beer, with the goal of producing a "cleaner" beer. In summary, and ultimate effect, to kräusen a beer is to add carbonation to it.
Krausening and Homebrew
Commercial brewers have far larger budgets than their homebrewing counterparts. As such, Krausening isn't always a favored (or budget-conscious) technique used by nanobreweries and DIY/Garage homebrewers.