Some of the criticism of how the current maternity and parental system works is that it does tie itself to employment. As some people pointed out, it is employment of a certain type. I believe the original motivation for integrating into the EI system is that childbirth does create an earnings' interruption, and the EI system in Canada has always been based on that idea of an earnings' interruption. When you look at the broader goals of maternity and parental leave, they have a lot more to do with health and welfare and child development than they do about the more traditional goals of the EI system.
If the idea is to support parents after birth, one could imagine a system that was completely separated from the fact that someone worked or not. One could argue about why all children don't deserve some sort of support when they're born, and for that matter, why not just give a lump sum? For example, in Australia when you give birth you receive a cheque from the government. You can argue about the amount, but it's a cheque from the government and it goes to everybody.
You can view that as a maternity leave benefit that comes in one payment rather than spread out over several weeks, and it isn't conditional on whether you work. It seems a lot of the argument here is about how much you actually have to work to get this. You can work this much or that much less. Particularly if you think of this as a policy directed at child development--given that there is good research that suggests that this will have a positive effect on child development, and my personal opinion is that it's not all there yet, but suppose that it was there and that's what you wanted to do--you could see the argument for just getting this part of the program out of EI and have a separate program for the support of families that are giving birth. It's always been, I think, an uneasy graph, given the sorts of criticisms that are often made at the program. As I said, I think it had its origins in the fact that obviously giving birth creates an earnings interruption, and this program is about earnings interruptions.