I've worked with some really good product managers, as well as some total duds. They all talked to customers on a regular basis. There is so much more to the job than that. Every time I think I understand a product manager's job completely, I see one fail in a way I hadn't thought about.

For example, I had one product manager who made themselves irrelevant because they wouldn't work with sales. The company needed to sell the product to pay us, and sales talked with potential buyers about what might swing their purchase decision and what they would pay extra for. Since the PM only talked to users and ignored sales when doing product design and product roadmaps, the way sales input got integrated into product development is that we frequently got top-down directives from management to prioritize one-off requests from sales over the roadmap. Needless to say, this didn't lead to a cohesive and easy-to-understand product.

Before I saw that PM failing, I hadn't thought about the relationship between product and sales.