Why is marketing so hard for engineers?
Short answer
Because the two disciplines reward opposite instincts. Engineering rewards precision, completeness and describing what a thing is. Marketing rewards compression, repetition and describing what a thing does for someone. Being good at the first actively interferes with the second — the more accurately you can describe your system, the harder it is to say the one blunt sentence that makes a stranger care.
The longer version
This question comes up inside a longer piece on the same problem. If the short answer above raised more questions than it settled, the full article has the reasoning behind it.
Why Developers Can't Market Their Products (And What Actually Works)