Could landlines be a necessity? The AT&T outage shows why cellphones alone may not be enough.

Like so many other phone users, Lindsay Woods ditched her landline some years ago and now relies solely on her cellphone. But after last week’s AT&T T, -1.19%outage, the Oregon resident is starting to have second thoughts. Woods’ concern? As a veteran publicist and marketing professional who runs her own firm, she wants to make sure she can always be available to clients. But even more important: Woods has a medical condition that could necessitate an emergency call on a moment&r