That's not entirely true. I get called on all the time, within my department at Google, to start things. Usually I'm explicitly forbidden from finishing them (even when I want to), either because they're "good enough" unfinished or because they can be handed off to other people who are not good at starting things.
The ability to look at a vaguely specified problem and say "Okay, here's how we're going to attack it, and here's what we need to build to have something that works" is a very valuable skillset, and not everyone has it.
Now, remember that "finished" is not the same as "launched". Usually, my responsibilities continue up to the point where we can get a product into the hands of users and train the people who'll be maintaining it after me. But there's a fairly large role for maintenance programmers, people who are responsible for little tweaks even though the system is mostly working as desired, and if you're a Starter, there's no reason for you to do that work yourself.
I think that your job sounds like a prototyper, which to say that your mandate is to develop to a level where others can rebuild it with a point of reference. Hence you're a starter and a finisher.
The ability to look at a vaguely specified problem and say "Okay, here's how we're going to attack it, and here's what we need to build to have something that works" is a very valuable skillset, and not everyone has it.
Now, remember that "finished" is not the same as "launched". Usually, my responsibilities continue up to the point where we can get a product into the hands of users and train the people who'll be maintaining it after me. But there's a fairly large role for maintenance programmers, people who are responsible for little tweaks even though the system is mostly working as desired, and if you're a Starter, there's no reason for you to do that work yourself.