Because this is 2016 and he doesn’t want to run for president?
The man is 72 and has been in government for 45 years.
Huckabee running might be a smoke screen, as leaving Fox could signal loss of viewership and the timing is good...he can always decide not to run and retire. He was a Governor and wouldn’t he have a retirement from that, or not?
He may run in Primary to test the waters...I don’t see him as a serious contender.