I think the simple answer to that is not many lenders will loan against the equity of the business they want bricks and mortar security and most small business would be borrowed fully against their home already.
Some have been smart enough to get their business property into super via limited recourse borrowing thus freeing up their home for other purposes, however that depends on the amount of super you have as most banks will only go 60% against business property (depending on what it is of course).
