Dunning-Kruger effect to some degree. A lot of people well versed in at least one field tend to end up thinking they're also well versed in everything else as well, so you get a fair few scientists who think they also know everything about the humanities and social sciences. Or people well renowned in one field of science thinking they know a ton about a completely unrelated one (see, many 'Intelligent Design' advocates).

There's also a certain amount of disdain towards it from scientists who seem to think philosophy has been replaced by science in general. Which is perhaps true in some things, but not so much in a lot of others.