When would it make sense for someone to get a domain name?

If you're self hosting services on your own network it's often easier to use a domain rather than have to keep up with home IP address changes. Same if you need to set up some sort of remote access into your network.

Also useful for email, you'll have infinite amount of email addresses you can use on your own domain. Plus if you ever need to migrate to another email provider you simply point your domain to your new email provider, you never lose your email address this way.

There is also social media that you can use your own domain to show you own your account. e.g. seems to be common at Bluesky.