According to the TSA’s news release about this issue:
Due to an increased threat to aviation security, DHS Secretary John Kelly announced in late June new security requirements for nearly 280 airports in more than 100 countries. In an effort to raise the baseline for aviation security worldwide, TSA continues to work closely with airports and airlines to enhance security measures and stay ahead of the evolving threat.
As new procedures are phased in, TSA officers will begin to ask travelers to remove electronics larger than a cell phone from their carry-on bags and place them in a bin with nothing on top or below, similar to how laptops have been screened for years. This simple step helps TSA officers obtain a clearer X-ray image.
Travel + Leisure reports:
The new regulations were tested in several airports earlier this year and will now apply to passengers traveling to, from, and within the U.S., according to a press release. TSA pre-check members will not need to comply with this new rule.