While you don’t have the speed of a skimmer, you do have the ability to deep strike right in, often on your opponent’s back line which is prime tank shock territory. Most players, like pinning, and leadership tests, can’t see tank shock in their head and they don’t account for it. When they do get it, again, most players are hesitant to death or glory that melta/las/power fist mode- especially against a monolith. Living metal, AV 14, and ponderous negates pretty much everything. If they are on the back of the board and fail, they run off- meanwhile you are also firing the flux projectors. Even fearless troops have tank shocking monoliths since it can push them off objectives and use the complete footprint of the model to contest it no problem.