The text is usually available in many other places, but the formatting here is (or should be) much better than what you get with automatic conversions. Often our books are also additionally proofread, include illustrations, etc.
To quote from our
General Book Uploads Posting Guidelines:
6. Uploads here should add some notable "value" to a PG (or whatever) original (for example: nice reformatting, artwork, a TOC, footnotes, etc etc). There's really no point in posting here something which which a poster can get from the original source in two minutes.