One of the fundamental aspect of developing continuous improvement culture is 'Empowering the People' and involving & engaging people across hierarchy to be part of improvement journey. So when we look at the stages of quality evolution is any organizations, it always passes through these 4 stages -
1. Ad-hoc fire-fighting
2. Single, stable quality processes
3. Integrated quality system
4. Quality excellence
The Kaizen is used to involve employees in this evolution journey and improve the overall organization especially in stage 2 and 3. Even though we look for ROI in a typical L6S world, but many of the Kaizen projects may not directly provide the ROI, rather they may lead to the areas where we can generate better ROI. For ex: Kaizens are done on standardize & harmonizing the processes, establishing process controls, deploying operation basics such as VMS, Tiered accountability structures etc. So ROI is always preferred, but may not be a primary goal when it comes to Kaizen. But people empowerment & engagement is a primary goal of a Kaizen way of working!