Many Bible software products are sold as packages that can be supplemented by purchasing additional titles as the need arises. The package price is cheaper than purchasing individual titles, though there are always titles included in the package that will not be used by everyone.
The relatively low cost of the packages provides students, pastors, and missionaries the opportunity to build a modest library at a cost cheaper than purchasing printed books. It should be noted, however, that purchasing additional titles may not be as cost-effective as purchasing a package. For a variety of reasons an electronic title may be more expensive from one publisher than another. In fact, sometimes it may be cheaper to purchase a printed text than an electronic text.
When the need arises to purchase additional titles for a new area of study, there often are electronic titles available for purchase. Usually these titles are available for immediate download. There is no longer a need to wait days or weeks for a title to be delivered. This benefit is especially useful for students who may not be able to access a book in the library for an assignment due in a couple of days.
There is little reason not to have a good, useful electronic library for your immediate use. You can obtain good titles right away for your study needs even if you are away from home.