A smaller deposit means less equity, and that can be risky
If you buy a home with a 5% deposit then you start the mortgage only owning 5% of your home. The rest is debt. If you make repayments on the loan, the percentage of debt shrinks and the amount of the property you own grows. This is also called equity.
But what happens if you can't make repayments, or you need to sell the home suddenly? What happens if property prices fall? In these scenarios, owning a tiny part of your home is risky. You could find yourself in negative equity. You could sell the property and end up with nothing.