Orcs and half-orcs have Powerful Build, doubling their lifting and carrying capacities. A Halfling, meanwhile, cannot properly wield weapons with the Heavy property. So even if a Halfling has higher STR than an orc they won't be as strong unless the gap is huge.
Also, even WITH Racial ASIs a max-level Halfling and a max-level Orc are equal in STR. Both hit 20 regardless.
5e is a bad system for trying to represent extreme strength disparities based on its attributes alone. The attributes are too abstract.
