Takealot - ebucks not earned

After checking my ebucks I discovered that I did not earn any on some purchases. After many emails and calls with eBucks, they discovered I did not use my ID no when I bought the items. So if you dont enter your ID no and ask to earn ebucks you don't get them. Please tell me why I would not want to earn ebucks ?! Why do we not just get it automatically like other purchases ? So nearly 8k worth of ebucks not earned.