WordPress is an open-source content management system. You don't pay a license or a subscription for it, and the site sits on your hosting together with its code, database and all the copy. We build stores on WooCommerce, the ecommerce plugin for the same system.
The reason is practical. WordPress is the most widely used content management system in the world, so finding a developer for it is easy. If we ever stop suiting you, another contractor can pick the site up, and nobody has to rewrite it from scratch.
There is a downside you should know about before we start. The system and its plugins need updates, and the site needs regular backups, or within a year or two it becomes open to hacking. You can do this yourself or hand it to us as website maintenance.
WordPress isn't right for a service with customer accounts, complex calculations or real-time booking. That is web application development, and we don't take it on. If your team is used to another platform, say so in the brief.