In an enterprise where architecture defines more than standards but creates governance so that many projects work together over time, cross project integration is much more a mandate than a target of opportunity.

Consider the need for a cohesive identity management scheme. If each project determines its own authentication/authorization mechanism you will have many wheels re-invented, variances in capabilities, and nightmarish regression testing issues (not to mention really annoyed users).

Extend this to issues specific to a domain, say managing shipments of completed products, and you may miss a better idea identified by a single project team who broke the political code to integrate with a package handling system, or for lack of communications across projects you may find the various approaches implemented end up costing the customer more and fail to improve the customers overall business.