The deck stepped mast is sometimes necessary when you live or moor in areas where there are bridges that don't open and are a tad low. Thus if your mast is mounted on a tabernacle, you can lower and raise it to pass under those bridges. Pease note that the tabernacle is well secured to the vessel. Plus there are a lot of sail boats that are trailered to the summer weekend launching ramp at their favorite lake or bay and the need to raise and lower the mast easily is a prime importance.
Have fun sailing.