What can a financial institution Frequently do for a deficit economic unit (DEU) that it would have difficulty doing for itself if the DEU were to deal directly along with an SEU?

SEUs usually want to supply a small amount of funds, whereas DEUs typically wants to acquire a large amount of funds.  Thus it is frequently difficult for surplus and deficit economic units to come together on their own to arrange a mutually helpful exchange of funds for securities.  A financial institution may step in and save the day.  A bank, loan and savings, or insurance company can take in small amounts of funds from several individuals, form a large pool of funds, and after that use that large pool to purchase securities from individual businesses and governments.  (This is just only one instance of the beneficial things financial institutions do for DEUs).