Pockets of emptiness in star fields?

This is probably a dumb question but I haven’t been able to get a straightforward answer from Google. Why is it that in any astrophotography image containing lots of stars in the background, there seems to be an unequal distribution of stars with what look like pockets of empty space? I just figured that given an infinitely vast number of stars/celestial objects and near-infinite amount of distance away from the Earth these objects can be located, we would see them as mostly evenly distributed. I’m intrigued by what look like line patterns of stars and areas where there’s almost none at all. Is this just a simple fact of gas/dust being unevenly distributed in the universe and it shows up pretty obviously in photos? You see it in any astro photo but here’s one of my DSLR photos that made me curious about it in the first place. https://imgur.com/a/pkjo4ew