Sometimes it's helpful to have some division of labor between field/sales/support engineers who go to handhold customers, understand their particular problems, and prototype fixes, and "product engineers" who have less customer interaction. This is somewhat similar to the SRE/SWE split at places like Google.
If I were designing an organization with such a division of labor, those wouldn't be different job descriptions but different activities within a single job description; maybe I'd spend 22 days a month doing product-engineer stuff like adding features, and 3 days a month doing support-engineer stuff like visiting customer sites, diagnosing customer problems, and answering calls, while maybe hatchnyc would prefer to spend 22 days a month doing support-engineer stuff and 3 days a month doing product-engineer stuff. The reason is that, doing either activity, you gain an enormous amount of knowledge that's crucial to the other activity, but very difficult to even put into words, much less into a knowledge base.
If I were designing an organization with such a division of labor, those wouldn't be different job descriptions but different activities within a single job description; maybe I'd spend 22 days a month doing product-engineer stuff like adding features, and 3 days a month doing support-engineer stuff like visiting customer sites, diagnosing customer problems, and answering calls, while maybe hatchnyc would prefer to spend 22 days a month doing support-engineer stuff and 3 days a month doing product-engineer stuff. The reason is that, doing either activity, you gain an enormous amount of knowledge that's crucial to the other activity, but very difficult to even put into words, much less into a knowledge base.
Bill Gates found it useful to answer tech support calls as late as 01989: https://www.entrepreneur.com/article/289857