Time and money
The information is always available at your fingertips. No need to call Directory Enquiries, look for any book, hunt for a CD-ROM, or ask anyone else to find the number. It's much quicker to click on the Directory icon yourself.
You can copy information into your other applications, such as addressing letters.
Do you need to find your way to a court or chambers? Print out maps that show the court buildings, car parks, railway and bus stations, main roads etc. No excuse for you, your clients, or your witnesses to say they did not know how to get there. And for "added value" to your professional service, there's nothing to compete with that!
That is just one of many small examples. As a search and research tool, as a "contact" information resource, it is unequalled for breadth, depth and usability. Firms use it to support the franchise audits, and chambers to support their BarMark applications.
You can fit a libraries worth of information on your computer and take it anywhere you go if installed on a laptop, so there's no need to carry books around with you or bits of paper with scribbled numbers or addresses on.