Each interaction with a user and each transition of an organizational boundary is an “ask”. i.e. the system is asking for the cooperation of some external entity. Users are typically being asked to cooperate by entering information into systems. Parties on the far end of integration points are typically being asked to cooperate by turning around information requests or initiating information transfers.
It is a worthwhile exercise while creating an architecture, to tabulate all the “asks” and identify those that do not have associated benefits for those who are performing the asks.
Any entities interacting with the system that are giving more than they are receiving, are likely to be the most problematic to motivate to use the new system. In my experience, looking for ways to address this at architecture time can be very effective and sometimes very easy. The further down the road you get towards implementation, the harder it is to address motivational imbalances.
If you don't have an answer to the “what is in it for me?” question, for each user interaction and each integration point interaction, your architecture will face avoidable headwinds both in implementation and in operation.