Banks are not permitted to act as investors in private placement programs, but they are able to profit from them indirectly in various ways (firstly getting big commissions).
This fact permits some private entities like private investors, brokers and trading groups to take part in this lucrative business that otherwise would be a banking matter only.
The private assets coming from private investors are necessary to start the private placement program process. These private large cash funds are the mandatory requirement for the buy/sell transactions of banking debt instruments and, as a consequence, also the mandatory requirement for the programs through the Trading Groups. Brokers/intermediaries are necessary to introduce the investors to the Trading Groups that exist.
Because of this, each of the involved entities share the benefits of these private placement programs (commissions for banks/brokers and proceeds for Trading Groups and investors).