VirtualBox provided an apt repo before Oracle (or was it Sun?) bought them. So they already had the infrastructure set up for providing apt packages. No reason

VirtualBox provided an apt repo before Oracle (or was it Sun?) bought them. So they already had the infrastructure set up for providing apt packages. No reason to dismantle it after the acquisition. In contrast, I don't think Oracle/Sun have ever provided debs for Java, so doing so now would require an investment of time, effort, and community collaboration to ensure that their debs incorporate themselves correctly into the system (via "update-alternatives" and such things).