Because if she recovers and can SAY that she was STRANGLED, BEATEN and GIVEN INSULIN SHOTS to cause INSULIN SHOCK---ALL designed to KILL her---then "LOVING" Michael would be CONVICVTED of ATTEMPTED MURDER and get LIFE IN PRISON or the DEATH PENALTY!!!
"LOVING" husband Michael MUST have Terri DEAD!
Or, for that matter, suppose there's other criminal malfeasance on the part of Michael, Felos, and Greer would could only be buried with Terri dead. Seems to me that if shown that could be enough for attempted murder right there (though that case would drag trough appeals courts for milenia).