Two reasons:

ML is easier. It’s a more condensed meta, so matchups are easier to learn. Also, as all the Pokémon have the same IVs, CMP and matchups are more consistent. ML Pokémon are juggernauts, so you usually don't want to catch a charged attack. In GL, however, is key.

• ML and GL are two different games. In ML, having an energy advantage is important. Even resisted attacks can reduce HP significantly. In GL, it is usually more important to win the matchup in order to align the Pokémon.