I think the biggest drawback is having self-published work taken seriously, although slowly that is beginning to change.
Agents sift through large amounts of poorly conceived, poorly written work (though in their zeal they often throw out the baby with the bathwater). Publishers weed out further in terms of what the pulbic is after, and their editors ensure that work is coherent and lisible, and in the case of scientific books, solidly referenced by the time it reaches the public. The entire rigorous process offers readers an invaluable service by ensuring that, at least theoretically, only the best work gets published. Granted, great work sometimes gets left by the wayside, but overall, people who buy self-published books are taking a much bigger risk when they buy self-published books and they know it.
Authors especially are taking a risk by self-publishing. Unless they excel at self-marketing, even if the book is a masterpiece, it won't sell. If it doesn't get great figures, they'll burn any bridges publishers & agents for the future (who are categoric about it) even those who might previously have considered the work for publication.
Think carefully before self-publishing. It's one of those roads you can't turn back on.