Don is correct except that the cross webbing is stronger than pure shear web. Look at any old iron briges. They used links, not webs. The grain aligns the strongest direction of the wood where it is needed.
Also, it is lighter an easier to fit in, and if you look closely, one link is ahead of the spar, the other is behind, forming a nice box structure with minimum weight. Clearly it is way lighter than carrying the sheeting out farther, and reduces the stress concentration at the end of the sheeting.
The only reason not to carry it out farther is pure lazyness!