I use my landline number for things like registering for store discount cards, or anything else which might tend to draw telemarketers. If I got rid of my landline, I’d start getting those calls on my cell phone.
I also use my landline to give as a contact number when one is required but I don’t want to give my cell phone number. But I have the ringer turned off and it is connected to the fax line on the all-in-one printer auto-answer. I can review missed calls to see if there was anything of importance.
The phone line is part of the cable bundle so the cost is minimal. I like to use it on speaker for outgoing calls as the quality is much better than the cell. Plus I still use fax for a number of items.