What's the use?
As scientists, much of our research is paid for by the public. If we choose not to communicate with that public, we aren't honoring their hand in the discoveries we make. Aside from the monetary, I'd argue that science is meaningless if it isn't shared. This is especially true for Astrophysics, as most of the discoveries we make won't impact people's day-to-day lives. The point (for myself at least) is to serve humanity's curiosity by answering the questions that humans have always asked: what else is out there, and how did any of this get here in the first place?
On a personal note, I wouldn't have attempted a career in science without following the lead of science communicators. Unlike what Hollywood may tell us, most scientists aren't born with the intrinsic knowledge that they will one day pursue a career in science. Most of us are just people who found an interest and made the decision to follow it. The world is brimming with people who may not consider science as a career solely because their idea of a scientist has been informed by the Hollywood trope. Science communicators find those people, keeping the field alive and diverse.