POS: the ledger
Foodics, Square, Toast. The POS is the single source of truth for what was sold, when, and for how much. It usually does not know who bought it, unless loyalty hands it an identifier.
CRM: the contact sheet
A CRM stores names, emails, phone numbers, and maybe tags. It does not fire campaigns on its own. Mailchimp is a CRM with a send button bolted on. HubSpot is a sales CRM dressed up for marketing.
A CRM without a connection to the POS is a static address book. It cannot tell you who lapsed last Tuesday.
Loyalty: the behavior engine
A loyalty platform is the layer that ties the three together: it captures identity at the POS, writes it to the CRM, and triggers the right message at the right moment. Without POS integration it is guessing. Without CRM it has nowhere to send. Without the trigger logic it is just a points app.
Habitu is that layer. The POS is your ledger, the CRM is your address book, loyalty is what makes them useful.