Banks grant loans based on your credit history.
If you can't prove that you can manage credit well, they can't know for sure and you are most likely going to end up with a 90% bond at a bad interest rate, or even worse, no bond approval at all.
Banks build fancy models and scorecards to determine who gets loans and at what rate, obviously it cannot predict perfectly. You might manage your finances perfectly and never had any credit before in your life, but somebody with the same credit score (or probability of default) as you might be terrible, and there are far more people in this category than you. What other option does the bank have but to offer all of you the same interest rate pricing and loan % options?
The losses banks sustain when an account goes bad (handing over to legal, reposession and finally sheriff's auction) are huge. So only giving 90% loans to most clients is a way of protecting itself. Can you blame the bank given the effect the financial crisis had? Homes that were bought for R2m (with balances outstanding of R2.5m+) are being sold at distressed sale auctions for less than a million.
My advice is sign up for a few store cards (the 6 months no interest type), buy on them, manage it properly. Get an overdraft on your cheque account even if you don't need/use it. Get a credit card and manage it properly (Pay full balance outstanding before your due date and you'll pay no interest).
All the banks are doing 100% bonds to their better clients. Be one of them.
I know the HL business rather well, so feel free to ask more questions should you have any.