Can't really explain it...but she kinda looks like a mother to me. She just has that distinct look. And personally I think she would make a good one. I'm not criticizing the fact that she isn't...I just wanted to point that out.
And besides, many of her female buffy co-stars are now parents (Sarah, Charisma, Alysson)...so it just surprised me a bit.
Eliza may have the look but not the maturity to be a mom in my opinion.
All you have to do is look at the long list of douche bags she's dated over the years and you'll see exactly why she's not mother material.
Or, she could be ultra self aware, knows there are a lot of douchebags in the world (from first hand experience), combined with the fact that there are way too many people here as it is, and has checked her ego enough to not buy into that "passing my (important, or so everybody seems to think) genes on" crap that everyone loves to spew when asked about wanting children.
Kudos to anyone who doesn't add to overpopulation, or at the very least stops at 1.