Why this is a service and not an afterthought
Every other service here changes your site. This one keeps it working, which means it is judged on nothing happening rather than on visible output. That makes it easy to skip and expensive to have skipped: an expired certificate, a failed update or a silently broken form is invisible to you and obvious to every visitor. The work is monitoring, patching and testing on a schedule, and it is priced monthly because that is genuinely what it is.