And there is plenty of research demonstrating that this is exactly what they do, and that doctors are indeed swayed by it, because, as you say, they don't have the time to do keep up with it all on their own.
And yes, there is a fundamental difference to consider here: My doctor has a fiduciary responsibility to do what's best for my health, to the best of their ability, and drug marketing compromises that. By contrast, nobody has any fiduciary responsibilities related to which brand of toilet paper I use.
