2 reasons, really.

First, yes, you'll get adhesive into those seams ANYWAY...why add the extra weight of yet more glue?

Second, any glue in those areas won't compress as well as the wood, and won't be as easy to sand...resulting in 'ridges' along every joint.

If, instead, the sheets are put together, and then taped in place (tape on the outside surface), they'll seal up nicely, and then when the tape is pulled off, sand and finish just like the rest of the surface.