Because not enough people understand the constitution or the impact of any changes. That won't be improved by the pressure groups who will come out and flat out lie about the impact changes will have on everyday life.
I can't decide if it's a good idea or not yet. Concerns are special interests and I don't think that the biggest concerns namely the economy can be fixed by rewriting the constitution. I think that the state relied for too long on the auto industry and we are just in for a rough road. But I'm still thinking, I haven't made up my mind.
The major problem with a Con-Con would be who the representatives are. There is a concern that it would mostly be term-limited state/senate representatives, given the likelihood of name recognition during the process to elect the con-con board members.
That could be a double-edged sword, on the one hand they'd understand the process, on the other, it would definitely politicize the process even more.
There are issues in Michigan which need to be addressed, but there is a real need to stay alert as to who becomes involved, and whose vast pockets will be spewing out money to influence the outcome.