I don't have a landline and you can tell I don't have a landline because I call wired, home-based phones "landlines" instead of phones.
I do, however--have a lot of phone books. Every six months, the DEX people swing by and drop off a stack heavy enough to hold my door in a wind-storm. My kids kick them off the front porch into the bushes and I throw them away. I switched to cells years ago. My husband spent a lot of time on the road and it was the perfect way for us to stay in touch.
I'm not an early adapter, but I'm also not a technophobe. My phone tells me if someone called, takes messages, reminds me about homework, surfs the web and has all the 2008 RWA lectures loaded on a storage card in case I get bored.
One thing it doesn't have is a listing in a residential phone book. There's no way a cell phone book would stay current. People buy disposables and throw them away, get new phones, add lines, end service, stop paying. It's a logistical nightmare.
But I still see plots where the hero finds the heroine through the "phone book", or "calling all the same last names in the phone book". It's an instant turn-off.
Technology changes. It helps to be aware.
Romances have characters in the 18-38 age range and people need to be age-appropriate. A twenty year old doesn't have the mental processes of a much older person. My daughter has a cell. If she wants to find someone, she checks a free on-line people-finder. You can make anything happen if you justify it, but when you don't justify it and go on outdated assumptions, it showcases the best years of your life, even if it was forty years ago.