Consumer apps such as Facebook, LinkedIn, Instagram, Feedly, typically pick up trigger events from the user's account. For example, the recipe will be triggered by new posts on the user's Facebook wall and new item in the user's LinkedIn account etc. This is because these apps do not have enterprise accounts, and connections to the apps are using the users account credentials. Even Google apps like Google Sheets, Google Contacts and Google Calendar operate at the user level. Even Salesforce can work at the user level, or the user's permission level.
For some apps, the recipe has to pick up data for all users of the app, for example you may want to move all the new employees from your HR system to the TimeSheet or Payroll system. To do this, the administrator will create an 'Integration administrator account' or a 'Integration User' and use that account to connect to the app. The integration account is a highly controlled, privileged account that will have permission to access all data for the enterprise. When the recipes are started with this Integration user's permission you will be able to pick up all the new employees, since it has the right permissions.