What are the Benefits of being in a Group?

What are the Benefits of being in a Group?

Morale, cohesion and the ability to launch a charge with the full line and thus avoid fighting one-on-one individual fights with outnumbered, unsupported and isolated units.

Also consider countercharges and other reactions.

And essential for impetuous troops if they want to win/survive

The group checks in one roll for discipline e.g. if you have moved a second time. Then the bonus of an attached general applies for the whole group. Moreover it is very likely that in case of a melee you get support bonuses or multiple melees.
then you can charge with a group together an hence avoid having to many opponents vs. charging with a single unit.