Current situtation:
Project for the Web is missing core, 'old school' MS Project functionality, such as sub-projects and cross-project resource planning.
Further, projects in Project for the Web is also incompatible with "Project Online" / "Project Desktop", the 'higher tier" (=$$$) version of Project.
Therefore, for a business to improve their overall project management approach, the business either needs to use a different project management solution.
...Plus it is confusing as all heck having two incompatible versions of Microsoft Project...
Proposed situation:
Provide a increased revenue generation pathway by making Project for the Web projects compatible with the higher cost "Project Online / Project Desktop" application.