Businesses take many forms and having multiple domain names, brands or separate businesses is common. Google Workspace allows you to connect several domains into the one account so you can send email from any of them, and the recipient will know no different. You can also divide up your staff into those brands (called Organisational Units) and provide different settings and access levels for each brand.
The benefit of this is having the ability to wear multiple business hats but keep control over your business without having multiple logins and subscriptions.