Hello,
macOS holds every approved system extension in its protected directory in /Library/StagedExtensions. This folder is covered by System Integrity Protection (SIP) feature and is writeable only to the OS, or to user in a Recovery Mode. So one possible solution is, that you were using your mac in a recovery or single-user mode and made some changes affecting this.
On macOS 10.13. Apple has a bug, that the rights of the staged extensions could sometimes get modified and the KEXTs were failing to load ever since (event after application re-installs). Apple never fixed it in macOS 10.13 and told us to encourage people to upgrade to macOS 10.14 Mojave, where the issue was resolved. From that I induce that macOS 10.13 is sometimes touching these files. It could probably happen, that the OS have somehow dropped your former decision to allow the drivers and that is why you see the dialog now.
Those are the only 2 explanations I can come up with. In standard macOS mode of operation, it is not legally possible for the user or for any application to delete the approvals. For more detailed info, you could probably ask Apple directly.
Kind regards,
Jakub