If you can live on one income and at least one of you has very low-risk employment and you have excellent good insurance, especially short- and long-term disability you don’t need as big an emergency fund as someone who is self-employed and self-pays medical care and has a lot of things waiting to break.
It’s no fun thinking about worst case scenarios, but they happen. A relatively common one is that one person is ill or injured, which brings the triple whammy of lost income, big medical bills, and higher living expenses as the partners’ time gets tied up with caretaking (and away from economizing, cooking, yardwork, and other savings)
Me, I’m a single mom with good insurance and a job in a somewhat volatile part of the high-tech industry, an aging house, and a somewhat special needs child. While I’ve survived four layoffs in four years, I take nothing for granted. I want to have enough to cover COBRA and job hunting and not have to panic. I’ve got six months in the FFEF and when I borrowed from it to fix the bathroom I felt really uncomfortable until I put every penny back.
Besides, that money isn’t going anywhere. I can always choose later to put some of it towards my kid’s college or into my retirement account. But right now, the lost interest is the price I’m paying for greatly increased security.