The Commission on Presidential Debates, which has definitely leaned Left, despite how supposedly non-partisan it is supposed to be, wanted to change the rules to a format that would favor, guess who? Joe Biden. After the first debate indicated just how unfair the moderator was to President Trump, why on earth would he submit to a debate in which a moderator could easily shut off his sound if he or she chose to do so? Why would he submit to a debate in which it would be so easy for Joe Biden to cheat? Or for the "moderator" to help him even more? As @guru pointed out, it is "disappointing but understandable" that the President would refuse to do it.

Biden campaign is running scared...