transferable lmi

Simple question, why is it that LMI ( Lender mortgage Insurance ) can't be made transferable?

For example, I pay company "xyz" a insurance premium each year but I can have my loan with any bank, credit union or building society I like?

Personally, this is the only reason I'm still with one of the "Big 4" because the compound interest in changing banks and paying LMI again isn't worth it (or so I believe)

I've always thought if the government really wanted to help people ditch their greedy banks, somehow they could address this issue.
Why can't it be done?

http://www.theaustralian.com.au/business/companies/commonwealth-bank-records-largest-profit-ever-for-an-australian-bank/story-fn91v9q3-1226696776311

*I'm not a CBA customer.