I've never been able to understand it, quite honestly. When I got moved to foundation, it was rather easy. The gap between foundation and higher is a bit too large IMO - the higher runs at breakneck pace, not allowing for time for things to settle in. Additionally, repetitive calculations are one of my pet peeves, and I really hate repetitiveness. Once, I got so frustrated (when I went back into higher) I got a nosebleed. Go figure.
Oh, and a lot of the material covered appears irrelevant to most people when they take maths, especially things like Surds. Without knowledge of their real-life applications, its viewed as 'pointless'. I don't even know what a Surd is used for in any job, lol. Trigonometry could be useful in architecture, but I've never been told that. A little extra detail could go a long way, as well as reduction in the material that has to be covered. Heck, if the exam papers were changed so you could do ANY (10) questions, then you could choose to do only those relevant to you later in life. That may help massively.