It fits how you already work. You install and manage the server the way you manage the rest of a client's stack, on Windows and IIS, Linux and Nginx, or Docker, against a SQL Server database.
The economics work in your favor. A one-time license means chat is a capability you own rather than a per-seat cost you pass through, which protects your margin as you add clients and agents.
You stay in control of the data. Because conversations live in your database, you decide retention, export, and erasure, and you can respond to each client's privacy requests without waiting on a vendor.