In the past years under the CFP, the #1 team was allowed to pick the location nearest to their campus to give their fans a better ability to attend.
This year, the CFP designated Dallas as the location for the #1 team so that more fans could attend (no fans were allowed for the Rose Bowl in Pasadena and only 3500 for the Sugar Bowl in New Orleans). The Dallas game (Rose/Cotton) is allowed 16,000 fans.