I agree, but it's also important to note that the relationship 'customer request' <=> 'ticket' is often not one to one. A PM will have multiple customer request

I agree, but it's also important to note that the relationship 'customer request' <=> 'ticket' is often not one to one. A PM will have multiple customer requests that slightly overlap, but not fully, and requests that make more sense as multiple tickets. In my experience it's really better to keep requests in a lightweight PM tool until they have garnered enough interest to write out as a ticket. The tool I use is Dynalist, really just a glorified todo app, where you can sort/collapse things that go together but there are a million tools like it. Only when there is some certainty it will ever be built does it get a proper ticket for the devs to look at.