Engineers have a perception that most other roles are lesser and if only they were allowed to be in charge things would go better. I certainly used to be this way. When I was an engineer I used to regularly engage directly with customers, and it was great to be able to talk with them one to one, address their specific issues and feel I was making a difference, particularly on a large product with many customers where you do not normally get to hear from customers much. Of course once these customers had my ear, the feature requests started to flow thick and fast, and I ended up spending way too much time on their specific issues. Which is just to say that I've changed my views over time.

In retrospect, the customers I helped were ones that had the most interesting problems to me, that I knew I could solve, but they were usually not the changes that would have the biggest impact across the whole customer base. By fixing a couple of customers' specific issues, I was making their lives better for sure, and that felt good, but that time could have been used more effectively for the overall customer base. PMs, managers etc should have a wider view of product needs, and it is their job to prioritize the work having that fuller context. Much as I felt at the time that those roles added little value, that was really not true.

Of course agreed that all the points made above for PMs, managers, support having their reasons to obstruct are true in some cases, but for a well run company where those roles really do their job (and contrary to popular opinion those companies do exist), things work better if engineers do not get too involved with individual customers. I guess Google might be a good example - if you have a billion customers you probably don't want the engineers to be talking to them 1:1.