Few of the advantages I can think of Landline phones are:

• No unnecessary bugging while you are outside or at a time when you want to spend some time with family outside home.
• No calls from office after leaving the office when you are outside somewhere.
• Cost of landline phone is quite less as compared to mobile phones.
• No time waste and addiction of being on phone all time, browsing social media apps/website, chatting and playing games.