In my previous home I had a Virgin set up that allowed me to have a dedicated phone line. I am elderly and a phone that works irrespective of Internet or power outage is important. My new home has the same hub as before but when the broadband went down today I couldn't make any calls.
Probably not for your convenience, indeed, (or any other customers for that matter!) but more to do with moving to newer technology and removing the need for providers to maintain and develop the old telephone systems and network. Same sort of customer 'benefit' as smart meters for gas and electricity!
Background info. in the first few pages of the OFCOM PDF document here (which is a fairly up to date link).