Domain jameslawler.com
I bought my domain jameslawler.com in April 2010 in order to "own" my presence on the Internet. I believe that a lot of people think that having a domain is only for a website, but I use it for a lot more than that.
I used to have a gmail account, but once I bought my domain, I setup all email to now go through my domain. Underneath I still used gmail to be the Inbox client (using the old, no longer available Google Workspace), but from the outside someone would send an email to my domain instead.
This provides me with a major benefit of email server portability. At some point I decided to minimise my usage of Google products from fear of being locked out of my account and losing all my email and contacts. I moved to a paid email service, so that I could feel comfortable being the customer and not being the product.
The classic saying still holds up.
If you are not paying for it, you're not the customer; you're the product being sold.
The move was really easy and I was up and running in the new email server with all of my old emails transfered over in only a few minutes. From the outside no one noticed as my email address did not change.
Website
Having a web presence can be important for building an online portfolio, or just have a way for people to contact you and keep up to date with what you are working on. Of course you could just use a social media service, but you don't really own that presence as you could lose you account at any time, or the service could shut down.
By running a simple website on my domain, I have full control of what content I want to show. Running a website can be done for free by using plenty of free services out there like GitHub Pages (if you are technical enough).
My current website runs on 11ty with TailwindCSS and you can check out the code here.
Sub domains
A nice benefit of having a domain is that you have unlimited sub domains that you can configure. For example I could create https://linkedin.jameslawler.com and set it up to redirect to my profile.