With the interdisciplinary work of agile/scrum, UX is not an integral part of product development. And therefore everybody’s responsibility.
“As someone who has worked in the field of user experience for decades, received training on half a dozen development methodologies, and completed over 150 agile projects, one thing that I am quite confused about these days is the term waterfall. In pre-agile times, I never worked in any organization that claimed they were doing waterfall development. If I did hear terms like ‘toss it over the wall’ – and they were as derisive back then as they are now. Product development – at least for products that anyone expects to be successful – has always been iterative, incremental, and collaborative.”
(Steven Hoober a.k.a. @shoobe01 ~ UXmatters)