Do you need territories?

Territories are important for your sales team. You can assign multiple salespeople to a territory, and when you configure CRM security, give them access to "My Territories." This setting provides the same access as "Mine", and will allow them to manage all accounts in the territory as a team, in addition to managing individual accounts as account managers. Refer to Creating or editing a custom security level.

Territories are also important for the Opportunity Detail report. If you do not associate resources with a territory in Autotask, you will not be able to select an opportunity owner to filter on.