While many other sites create a list of reason to use WordPress, this list will be kept short on purpose. Most people doing work to create and/or maintain their own web site are less interested in some of the reasons others will list simply to fill out a list. Here are the 5 biggest reasons I see to use WordPress over other self-hosted solutions or even many of the big hosted solutions.
Flexibility
WordPress, which is used on over a third of all sites, offers flexibility, both in terms of basic items such as themes and plugins, many available at no cost, while others are either free / paid or outright paid to use. In addition to these things, if one knows a little about coding with PHP for example, one could create child themes to allow for customization to happen without disturbing a parent theme's ability to update without overwriting changes. Also, one can hire someone to code a specific use plugin or theme features if no personal coding experience is available.
Ease of Use
WordPress Core, the main building block of WordPress comes with two options for working with content: Gutenberg and text editor. One can also bring back the ability to use the former visual editor with the use of the Classic Editor plugin. Alternatively, there are other free or paid visual editors, some bundled within themes.
Community of Support
WordPress comes with a huge community of support, from the forums at WordPress.org for plugin and themes found there, to external developers to various sites where one can post questions and get responses from others who are programmers or WordPress Developers. There are so many available choices for support, including here at I Do Web Work.
Hosting Choice
From using a hosted solution at WordPress.com, which is run by the company behind WordPress, to any number of self hosted platforms. Most hosting provides will support WordPress to some level, although not all hosting solutions are equal. Hosting prices can range from less than $100 per year, some even including the domain name, to hundreds of dollars per month, depending largely on the resources needed for your site.
Ownership
Owning your site's content, and all associated files, is huge. Many of the hosted platforms like Wix or SquareSpace do not offer the ability to export your content along with all the framework that makes your site look as it does. WordPress absolutely allows for you to do that, whether using the built-in content export or a backup plugin like the free version of UpdraftPlus. Most hosting platform will also provide a way to export site structure and content. For me, ownership and export-ability are huge, as sites might wish to be move from one host to another for any number of reasons.