The decorum in London and Tokyo dictates you don't talk to your cabbie and they don't talk to you. The drivers of the black cabs in London will not make small talk as a rule. It helps them focus on doing their job, and it prevents you from boring them with the 50th tall tale of the day. It certainly rubs the general American sentiment the wrong way but it has it's perks. In the case of this article the passengers would know they're expected to shut up until they return home, pay, and get out of the cab.
This isn't to say cabbies never talk to customers (emergencies, change of plans), but the expectation that you should ask every service professional you encounter about how their day is going and what are their hobbies and what's their favorite color isn't a universal value. Some people like the author actually find it a little irritating!