When to use quantitative vs qualitative data

I’ve been a huge advocate for gathering more data about how customers are using our products to drive better product decision making. In particular, I have focussed my recent writing on how to define better metrics and gather quantitative customer behaviour data as this is one of the biggest gaps I’ve seen in Product Manager skillsets. However, I would not do my job well if I didn’t also highlight the importance of gathering qualitative data to truly understand the motivations, frustrations or fears of customers.