As you're probably aware, most software through Linux is downloaded by way of repositories; and most development teams update these regularly. However, at the time of writing, the one offered on Krita's website (which, as an appimage, does not produce an icon or come up in search, which is inconvenient), is 4.2.6, and the one offered on the repository is 4.1.8.

Is there a reason why this seems to get updated so infrequently?

It's the distributions that update the software repositories; the Krita team has no power over their packaging. To get the latest version, just use the website.

If you are an ubuntu user use the lime ppa, which is handled by our community members. it will give you fairly latest krita

irina_r wrote:It's the distributions that update the software repositories; the Krita team has no power over their packaging. To get the latest version, just use the website.

I was not aware of this! Thank you.

To make appimages more convenient, you could also try AppImageLauncher:
https://github.com/TheAssassin/AppImageLauncher/

It handles all the desktop integration stuff so you can easily find krita in the app menu/launcher/dash or whatver the desktop environment you use calls it.
And maybe krita appimages get the ability to self-update soon(tm)...