a question about exec_simple_query()

Hi, everyone:

In functin exec_simple_query(), why we run a simple query wrapped in a portal.

For instance:

version 8.3.0 ,postgres.c, Line 908

/*
* Create unnamed portal to run the query or queries in. If there
* already is one, silently drop it.
*/
portal = CreatePortal("", true, true);

......

In other words, what's the benifit we use a portal to run a simple query?

Thanks for your help! :)