From what you say I assume that you think a publishing house's only job is to take your manuscript to the printer. Well, no, there's much work involved in the editing and design process prior to that. There's people working on the logistics and marketing of books. There're legal, financial, technical and administrative issues (as in any business). And paying all those, plus the books, costs money.

I don't know with which publishing houses you've been in contact with, and I think most of what you say comes from a bad experience with dubious publishers. But, in a serious one you work with an editor, whose job is to read your manuscript and tell you what's good and what can be improved, and how it can be improved. A good editor with some knowledge of the field your book is about is an enormous help.