Why'd the lender suffer the collateral haircut, not the borrower?
Why'd the lender suffer the collateral haircut 


This is not an accurate way of describing what is happening. No one "suffered". The collateral was entered at lower than current market value, to account for the risk. It can also be repossessed from Steve at lower than current market value.


  Why wouldn't Steve (the lender) assign the collateral haircut to you, and require you to pay him $11 + risk premium?


That would have also been acceptable to Steve. As it is explained in the text


  $1 seems like a lot of money for one day to you. But you do need to eat so you don't have a lot of options.


So it is in fact you who did not want to pay the risk premium, and Steve went along with your alternate offer.