WordPress keeps getting better, but only if you make the updates. For example, WordPress 3.9, which is just out as I write this post, has a much improved image processing module which makes it easier to edit pictures.
The most important reason for keeping your WordPress site up to date, however, is security. Just as the ones for your computer’s operating system, security updates come out regularly for WordPress.
If you have a free-standing WordPress site (i.e.: a WordPress.org website that is not part of a multi-user network such as WordPress.com, or a network that I administer for some of my sites), it’s important that you keep it updated. The bonus is that you get to enjoy new features as they are developed.
Plugin and theme developers have a chance to try a beta version of the updated WordPress core before it is officially released, in order to prepare their code to keep pace with the changes. Within a few days of a major WordPress core update, the better plugins and themes often have updates available. (When selecting plugins and themes, it is important to choose ones that are kept up-to-date.)
If you do not have administrator status on your WordPress site, you may recall seeing a notice in the backend to contact your administrator to update the site for you.
If you do have administrator status for your site, you can perform the updates yourself. In my experience, however, site owners tend to be reluctant to dive in and perform this function.
Updating WordPress has become much easier over the last few years, and minor core updates even happen automatically now.
It is a very good idea to do a backup of your site before making an update. WordPress will remind you to do that. There are a number of backup plugins you can use to either save a copy of the database on your site’s server, or send it to your email or to Dropbox, for example.
Premium themes (non-free themes) and plugins, which tend to offer advanced functionality compared to the free ones available, usually require a manual upgrade. This can involve logging into the supplier’s website, downloading a zip file, uploading the file to the WordPress site, activating it, then checking to make sure everything is still working well.
Whether you do your own updates or have a webmaster do it as part of their management services, making updates to your WordPress website is an important part of keeping up with this ever-evolving web we are weaving collectively.