My customer is looking for a Business Process Management (BPM) solution. What they need is simple document routing and an approval system. What are the drivers for implement
When you want to provide flexibility (easy changes) to the process, even for running processes.
When you want the business users to control the process. Those are the domain experts who own and define the processes. By using a BPM solution you allow them to control the process using modelling tools instead of programming languages. This is essential.
When you want the system to scale easily. Normally system admins would have the possibility to monitor and operate the system. If this should be possible also for business users, then BPM might be a good choice.