There are companies that negotiate a "no frills" corporate rate. No points no perks in exchange for a higher discount. Your client must be one of these.
Agreed. No harm in asking for a manager if you are going to stay a lot and negotiate some perks - the front desk staff might not be able to help you but if you have Platinum status a manager will probably work with you if you are a returning guest. Kill him/her with kindness, it opens a lot of doors.
Also, ask specifically why the rate excludes upgrades.