There's still a lot of ISDN in retail

Both dialup ISDN (V.120/V.110) in addition to routed ISDN. Hell, there's still a lot of async POTS dialup, even though that's degraded somewhat since ADSL rolled out.

Whilst most people are moving to IP - ADSL, SDSL, leased line etc, the central pipe cost can be very large if the systems need to be hosted in house and the head office isn't in a major city centre.

Sure, it's not fast, but it is generally reliable (except when it decides to disappear, especially on lines that haven't been used for a while)