When most academics publish in a reputable journal they do it because it increases their market value . I hasten to add that not all academics feel that it this the only reason for publishing. Publishing paper journals helps readers. The academic publishing artifact is a quality control device . The industry has established rules and methods that ensure readers can be reasonably confident they are not wasting their time reading an article.
Traditional publishing saves readers time.
However, most of the quality control rules and procedures are independent of the method of publishing. Editors and referees normally work for no payment. The mechanics of electronic publishing are very much cheaper than paper publishing. The challenge is to keep the quality control but remove the cost. One method is for everyone to publish in electronic journals.