There can be many reasons why your device doesn't have the latest updates. Maybe there is no current maintainer. Maybe the device recovery partition is too small for the recovery partition on the phone. Maybe someone reported an error with the live version of the recovery and it was removed from the site to prevent widespread issues.
Many times we get reports of unworking images that were released to our site. Unfortunately we don't have every device and rely on word of mouth to tell us when issues happen. Sometimes maintainers don't get a workable update. A lot of the newer recovery updates adds more libraries or other files that increase the ramdisk size past the limit of the recovery partition. Any of these reasons can cause a device's latest update removed from the site. Until the device can be updated/fixed, futher builds will be disabled.