Here is the twist: on iOS devices (iPhone, iPad), third-party browsers such as Firefox and Chrome must use Safari's faulty and outdated WebKit engine. Therefore, websites will experience the same bugs even if you use a different browser.

Suddenly you realise that Safari indeed effectively has a big market share - namely all Apple mobile devices browsing the web.

I just spent a whole day working around a very annoying iOS Webkit/Safari quirk (HTML button elements not receiving focus). I had to resort to user agent sniffing and working around from there. I haven't had to do such stuff for a long time.

Back in the Internet Explorer days, you could at least say "just use a better browser". With the Safari situation on iPhones and iPads there is no such choice. Installing Chrome just gives the browser a different skin with respect to the browser engine.