Alternative to Blurb to print Lightroom Books?

The newest version of Lightroom is fantastic, particularly the "Book Module". I love the layout options in the Book Module, but for some unexplained reason, it seems to only work well with a single source printing vendor, namely Blurb. While you can export the final layout as a .pdf, the  limitation created by the unique sizes makes it largely unusable with a printing service other than Blurb.   Is Blurb owned by Adobe, or is there some type of kickback arrangement here?  We all pay Adobe a fair amount of money each month, and it seems as though they should be looking out for our best interests, rather than a single source third party vendor.   I hope I am mistaken here, but if true, Adobe should come clean here and disclose the exclusive arrangement and make it clear that the "Book Module" is more of a third party plug-in from an outside source, and may only be fully functional if you use Blurb to do your printing. I have nothing against Blurb, but their pricing, and breadth of services and sizes is not competitive with other printing vendors. 

Are my concerns here misplaced? Is there a work around that would allow me to routinely use the layout functions in "Lightroom Book Module" with other printing companies?