3 of my 4 kids only use cell service, and they are find. I myself keep my ll for the following reason. Occasionally we've lost power for days and sometimes weeks. But, even without power, the LL phone service has NEVER gone down. Even the cell service has been out for short periods of time, or has had other problems. I just like the security of knowing that, if there is any kind of emergency at home, the phone works.
My office is in my home. And I have my office phone on the verizon fiber optic network. If we were to lose power, the battery back up will last for 8 hours. (We've lost power for much longer than that). But, my main house phone is the old copper LL. Eventually, verizon will end support for that. But, until then, I keep it.