It is entirely possible to drive some parts at a higher speed if you so wished, on a clear summer's day, I can absolutely see the temptation. But they don't have variable speed limits on that road, so on a murky rainy day, on a foggy day, on an icy day, conditions are very different. Given the huge number of non-regular road users (tourists, and also the day trippers from Vancouver etc. who are going up to Whistler) it would be darn dangerous for some of those sections to have higher limits - partly because some people think a speed limit is a target, not a maximum (and doing the limit in those conditions could be suicidal) and b) because the locals, the regular drivers who know the road like the back of their hand, and who have winter tires, decent winter road handling skills etc. would drive at the higher limit and that in itself, with much slower traffic on the road from drivers who are more cautious, would cause accidents. I used to drive a (different) road every day, and it had some wicked bends - I knew the road so well, I knew exactly where and when I had to brake to make turns - but the casual road users didn't, and there were a lot of accidents on one particular turn (the whole road was 60mph - the standard for out of town roads) and eventually they actually lowered the speed limit for the small section that included that bend. But a lot of people who knew the road far exceeded the new limit, and there was a hideous head on collision with a local overtaking a "Sunday driver" just before the bend.