Another possible reason is that Arnold -- seeing that "even" many of the Leftist-lature are sprinting away from the Reiner-smell -- is letting Meathead twist in the proverbial wind for awhile.
That would be a convenient excuse, today. But Reiner was appointed by Gray Davis in 1999; his term expired in 2003.
Here is what the statute says:
130115. The Governor shall appoint three members of the state commission, one of whom shall be designated as chairperson. One of the Governor's appointees shall be either a county health officer or a county health executive. The Speaker of the Assembly and the Senate Rules Committee shall each appoint two members of the state commission. Of the members first appointed by the Governor, one shall serve for a term of four years, and two for a term of two years. Of the members appointed by the Speaker of the Assembly and the Senate Rules Committee, one appointed by the Speaker of the Assembly and the Senate Rules Committee shall serve for a period of four years with the other appointees to serve for a period of three years. Thereafter, all appointments shall be for four-year terms. No appointee shall serve as a member of the state commission for more than two four-year terms.