Advantage for high ground is actually one of the situations used as an example that a GM can use to give Advantage to a person in the battle. GM's in the tabletop are given wide leeway as to what situations apply Advantage/Disadvantage. It's only listed as a suggestion/option because the more things you track the more you slow down gameplay on a tabletop. Computer games are just able to track all this stuff easily so it's easier to include it.
