This is because a significant amount of the cognitive labor involved in producing truth is codified in the scientific method, which every practitioner can be trained to follow. Philosophy has developed no such innovation.
Um... you do realize that PHILOSOPHERS developed the scientific method, right? That was not something scientists just came up with on their own. So, when you say that philosophy has developed no such innovation, you miss two things.
First, philosophy did come up with that exact innovation, for science.
Second, scientists have not come up with any such innovation, for themselves or others.
Why Talk to Philosophers? Part I. by philosopher of science Wayne Myrvold.
See also Sean Carroll's own blog entry, Physicists Should Stop Saying Silly Things about Philosophy.
Sean classifies the disparaging comments physicists make about philosophy as follows: "Roughly speaking, physicists tend to have three different kinds of lazy critiques of philosophy: one that is totally dopey, one that is frustratingly annoying, and one that is deeply depressing". Specifically:
He counters each argument presented.
Personally, I am underwhelmed, since he does not address the point of view that philosophy is great at asking interesting questions but lousy at answering them. Typically, an interesting answer to a philosophical question requires first recasting it in a falsifiable form, so that is becomes a natural science question, be it physics, cognitive sciences, AI research or something else. This is locally known as hacking away at the edges. Philosophical questions don't have philosophical answers.