I see your point.
I always worry about too much rigidity in budgeting. I worry that if you create a lot of dedicated funds and everything else, you do create that problem.
In the case of the CPP, I think it was quite wise to put it in a special fund, because there were federal-provincial aspects associated with that. I think there could be a case for EI if you really wanted to run it more like an insurance fund, just like workers' compensation programs at the provincial level, but I'm not sure I would like to start seeing a whole bunch of funds created for everything else. At that point I would be cautionary, just as your question suggests.