Why don't some staff accounts appear in the Salesperson drop down menu when creating an organization?

Environment: 

Organizations, Accounts, Profiles

Resolution:

Visibility for assignment as a Salesperson can be enabled/disabled at the profile level.  Use the steps below to resolve this:  

1. For affected accounts, open their associated profile for edit.  
2. Select Permissions from the top ribbon and then the Opportunities tab.  
3. Enable the Assignment - Appear in Menus option and save the profile change.  

When you create a new organization, all staff associated with this profile will then be available from the Salesperson drop down.  Note:  If you do not see them right away, you may need to log out and back into the application to test results.  Changes should be immediate.