Designers of document storage and mgmt apps (with large document objects) had to decide where to store the objects. These included document management systems like LiveLink, and more recentlySharepointt.
As internet bandwidth increases, applications that use large files are expanding, including video and music files.
LiveLink, as a document management system supported both (either) the storing of documents in the database as blobs, or in external files. As some of the earlier comments noted, large blobs were slow, so most installations used external files. That allowed the database, which then only held meta-data, be be fairly small, fast, and to only require a modest server.
Naturally, maintaining the correct linkage between the external files and the internal database records added some additional overhead. But not really any more than the double-linked system the database engine uses to maintain page consistency.
Filestream gives you an option, but like all options, only use it if it makes sense, and meets the business objectives. My guess is that for many cases, storing files completely outside of the database (the current approach), and only storing the metadata in the database will tend to be the best approach.
The more you are prepared, the less you need it.