Even if you don't plan on having a website.
Having your own domain has a lot of advantages. It gives you plenty of freedom and also helps you stay secured.
Infinite email addresses
The most important use you can make with your own domain is having access to an infinity of email addresses. You probably already have at least one @gmail.com, @yahoo.com, @hotmail.com, @whatever-free-email-service.com address, probably 2 or more, everyone does. However, none of these gives you as much freedom as having your own domain does.
For every service I sign-up for, I use a custom email address tailored to the website: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, etc. I never forget a login name AND in case I use the same password for more than one service (which has to happen with the 20+ logins we need nowadays), I'm protected against leaks from a service.
I no longer have one username/password combination for multiple websites, I have one per website, making each one unique.
You can move
If your main email address is email@example.com, then you can decide what to use to read your emails. Personally, I receive my emails in a GMail account, but you can use any other online email service or a regular desktop based software. If one day you decide you don't like what you like or a new email service pops up, you're free to go there without having to inform your whole address book that you're changing your email address for the ump-teenth time.
So you want to sign-up in some website, but you're not sure if it can be trusted. Surely, you don't want to use your main email account and risk of getting spam on that account forever. With the one email address per website, you're secured. If you do get spam from that address, then just filter them out.
Note that you can do something similar with GMail by using firstname.lastname@example.org (replace whatever by anything you want). However, some websites consider the plus-sign (+) as invalid.
Your web identity
If you have your own domain, you're just a step away from having your own website. You may not want to pay for hosting which costs quite a bit more than just a domain name (and is more complicated to manage too). In case you do not want to pay for hosting, it's easy to forward to a blogger account (and probably for many other similar services).
It costs money
At 6 to 10$ for a .com per year, I think you can afford it. At most you'll pay 20$ for a .me. So bring your lunch to work for a day or two instead of buying food and it'll cover the expenses.
It's really not, it involves a few steps but it's a fairly simple process even for non-tech savvy people:
- Find a domain name seller -- I use GoDaddy.
- Find and buy a domain name you like
- Set-up an email catch-all account
It should take you less than an hour of work (maybe a bit more while you wait for confirmation emails).
What are you waiting for?
There are plenty more reasons to use a personnal domain name, a few more are listed here. The benefits outnumber greatly the minor inconveniences.