Money. Hosting and backups cost ~$75/mo.
Also, security. We're on an old ass (and vulnerable) version of Apache and PHP and Ubuntu operating system that's 12 years old.
And time. I don't want to put the time to building up a more secure place to host such old shit, nor do I want to put the time in to fixing all of the stuff that breaks when performing an upgrade so it can run on newer shit, for a site that gets dozens of users a month.
I'm open to discussing handing things off to someone, if someone wants to put the money and time into bringing things up to current spec.