Today, September 30, is the deadline that Microsoft has announced for age ratings to be included in all apps that are published in the Windows Store. Any app that does not have an approved age rating risks being removed from the store after today.
Microsoft started rolling out the new age rating system for Windows Store apps in January 2016, based on the International Age Rating Coalition's (IARC) system. Ratings are also available for each market, like North America, Europe, Germany, Australia and Brazil. Microsoft has already sent out emails to developers who don't have these ratings on their apps, alerting them that they could be removed after today.
It's very possible that we could see a large reduction of apps from the store due to this deadline, especially from apps that have been in the store for a while but have not been updated for some time by their original developers.