I've been trying to tell to my grandparents that there is no point in paying for the landline because they have mobile phones too. Finland had full coverage of landlines but they are being abandoned at a fast rate because cellphones are just so much more convenient. Basically here only old people and businesses have landline phones anymore, others have no need. Also everyone has a cellphone (of course there's always the exceptions who are technically savvy but choose to be unreachable).
In my opinion, people who only got a landline and no need for mobile, are clearly people who spend most of their time home and so are not a great sign of development.
That may be true for some countries and some individuals, but not all. There are several good reasons to have a land line:
1. I hate carrying a phone around with me at home (and I don't do it). I live in a two story home and leave my cell phone in the charger on the first floor. I would miss a lot of calls if they went to my cell phone.
2. I have a cordless phone system with one base unit and 5 cordless units, so there is a cordless phone in every room. The cordless phone has an excellent speaker phone and it is very convenient. The phones are rechargeable, and if one of them has a battery that is exhasted I can just use another one.
3. In the USA there is an emergency number system (dial 911) that connects you directly to an operator to handle any police, fire, or medical emergency. As soon as you call them they know your name (or family name) and exact location, and this is the best way to get help in an emergency, especially if you are not able to give much information because of the problem. Although you can call 911 from a mobile phone, they won't know your exact location (only general area) and it takes longer for them to even get the approximate location.
I only use my cell phone when away from home, and I have instructed my friends to call me at my land line first because I may not answer the cell phone immediately (although I can usually call them back).
At least for DSL Internet users (as opposed to cable Internet), there is usually a discount given if you have both DSL Internet service and a land line (at most US phone companies) since it uses the same wire.