RRSP contribution limits are based on 18% of earned income in a year to a maximum of $26K today.  If as a small business owner you are drawing little or no salary while you grow your business, your RRSP contribution room is minimal or NIL for those years.  If and when your business is successful and you are receiving a good salary, you only have access to the current years'  contribution room.  

Also if your business has a hiccup and you need to put more money into it, taking that money out of an RRSP is expensive from a tax perspective and you do not get to put it back in ever again.

You may or may not have known that, but that is why it "isn't enough".