That’s not only a snotty comment, it’s a dumb comment. A babysitter can call you on your cell phone just as well as your landline. The only problem is if your cell is turned off (a dumb thing to do in itself if the kids are being sat) or being recharged. But then, if the two of you have cell phones, the sitter should have both numbers. Case closed.
So far, I’ve had no instance where I’ve needed a landline over my cell phone. And since most of our calls are between the wife and I, our 700 minutes aren’t an issue. While it would be nice if more of the extended family were with the same carrier, that’s really a minor issue with us.