Two reasons the answer might be yes:
1.) You get a higher AC. Who doesn't want a higher AC?
2.) It looks cool. I had a player design, but did not run, an updated version of the old Dwarven Battlerager with a Tortle, rather than a Dwarf, as the base. Essentially, he drilled and attached spikes and plates to his shell and attacked by crashing into things and gyrating. Mechanically, I told him it would be like he was wielding a greataxe (as his character could wield it), but allowed him to have his hands free (with an offsetting disadvantage). In the end he went with a different design, but there are now Shellshock Troopers in my setting based upon his ideas.