So here are some generalizations.

While in school, I noticed that the physics students were far more interested than the chemistry students, in math and computer stuff. Maybe we were computer science wannabees, or maybe we guessed (correctly in my case) that proficiency with computers would make us more employable. This was true in both undergrad and grad school.

And there's a long tradition of physicists stealing ideas from math and computation for solving physics problems. When I was in school, computation was considered to be a specialized branch of chemistry, but was at the forefront of physics.

Another difference is that the physics students were generally more interested in making our own tools. The current "maker" and "hacker" trends are old hat for small-lab experimental physicists.

Chemistry has always been a bigger field than physics, which I suspect has attracted more interest in making commercial equipment and software. I've noticed in an industrial setting, that managers are often looking for closed solutions that can't be modified by the user, either for regulatory reasons or adversarial labor-management attitudes. The industry wants your boss to think that letting you make your own tools is either dangerous, or a waste of your time.

In contrast, even in industry, physicists still have to make our own tools. And management already knows that we're freaks. ;-)

So the absence of FOSS tools for chemistry doesn't shock me.