The UK ( whence comes this article ) has a very competitive ISP marketplace, there are several dozen ISPs vying for my custom at my property using a variety of connection technology.
But most people in the UK sign-up to the Big Three ( BT Retail, Virgin, TalkTalk ) due to their intense advertising and bundle 'deals'. So those three consider themselves the market and compete with one another for that pool of customers. Naturally they make leaving difficult because they have spent so much on acquisition.
The other 20% of customers shop around based on individual requirements. I've been with my small, efficient ISP for 12 years and have no reason to change.
The UK ISP marketplace is not competitive. In most places you have no choice but to go with Virgin if you want half-decent speeds. The rest of the ISPs are just selling DSL which is crap compared to Virgin and there’s no easy way to tell how well it will perform in advance before signing up (it depends on the state of the wiring).