Of course it's possible to get by without a driver, but in certain situations such as the ones I've outlined, where one is living in a remote area without good public transportation and both parents are working, it certainly benefits to have one.
And yes, of course having a driver is expensive. Most people can't afford one, and that's fine. Everyone has to make due with what they have. If it was affordable, then most people would have drivers when of course, like you, they don't.
My whole point was that for the OP to consider living in some of the developments discussed on the thread, and his own comment about the lack of shuttle services and the like, is that almost everyone in those developments have at least a car and most likely a driver. Further to that, I was making a point that there is a cost of living to such developments, particularly in the gated communities in the New Territories, that goes beyond the cost of the lease. Him working in Shatin certainly makes things easier than if he was working in Central, and as another poster mentioned there is a mini-bus from The Beverly Hills to the Tai Po KCR which makes going to Shatin easy. Depending on where he worked, he would then have to take another form of public transportation or maybe just walk. I estimate that would be still a good 35-45 minutes door to door, whereas driving would take roughly 12-15 minutes.
If he had to work in Central, that would be a lot more difficult as it would mean taking the mini-bus to the KCR station and then the KCR to Kowloon Tong, then changing from the KCR to the MTR and then taking that train through many more stops including changing trains to get to Central. Perhaps there is a bus from Tai Po station to Central, but in either scenario, the ride would be mind-numbingly slow, no doubt taking at least 60 minutes if not more coupled with a lot of walking, when driving would take 30-35 minutes. I can imagine the vast majority residents at The Beverly Hills who own their own unit are not taking such public transportation on a daily basis, and certainly these developments were built with the idea that most everyone would have their own car and yes, probably driver.
I live in a house in Tai Tam myself and while there certainly is good public transportation here, probably better than at some of the developments that have been mentioned on the thread, our kids' school is not close and having to take public transportation everyday to their school and back would be difficult for them. As it is, every one of my neighbors all have drivers so I can imagine they agree.
Again, you can certainly "get by" in Hong Kong not only not having a driver, but even a car, but if you live in certain areas away from the city, it is definitely better to have one.