Another reason is for business. A lot of paper work is filed and signed in the White House or Oval Office, not to mention the many parties and meetings held there. If the president were not to live in the White House, he would have to fly to Washington D.C. extremely frequently to attend many business and social functions.
The final reason is for security and protection. If President Trump did not live in the White House this would mean body guards and secret service members would have to guard him in his own home . This would disturb people living around the president and would be uncomfortable for people in places where Trump is visiting (such as restaurants and other buildings).
Since President Trump is a successful business man he has made a lot of money over the years, and because of it, it has led him to buy several enormously large residences. He also owns many vacation homes and other business offices around the country. Some might say that President Trump should not have to live in the White House because he would actually be downsizing. Well first of all, whether he lived in the White House or not, President Trump could always travel to his houses specifically for vacation reasons so the vacation homes don't count. Now let me tell you some confidential information... The White House has more square footage then President Trump's house. The White House has around 55,000 square feet while the penthouse in Trump Tower where President Trump spends most of his time only has around 30,000 square feet. The White House is approximately 168 feet long and 152 feet wide. This large homely house includes "132 rooms, 32 bathrooms, and 6 levels to accommodate all the people who live in, work in, and visit the White House. There are 412 doors, 147 windows, 28 fireplaces, 7 staircases, and 3 elevators." Trumps Tower Penthouse has only 3 levels and sure doesn't have as many rooms as Trumps new home (the White House). So for all those people who think President Trump is downsizing... you're wrong!