No one will buy your IPO if its going to be at market price. You'll need to add a discount. Why buy from an IPO and do more paperwork when you can buy from the market instantly?

Also each time you sell shares in an IPO you need to have people make lots of calls to institutional and other investors to determine the demand and thus proper pricing and supply of new shares. Having to do this everyday will be expensive. You (as a bank managing the IPO) also probably don't want to pester fund managers too much (They have to take care of other stocks in their portfolio, too), otherwise you'll have trouble doing IPOs for other companies.

EDIT: I take that last sentence back, it seems like they really want those IPOs regardless if the bank is a vampire squid, or not.