You can't compare running a server like Snapcraft and your single player... yes, you can run Vanilla 1.8 in your own pc or maybe a small server with friends, but SC has a lot of plugins to create a unique experience...
What it means?... There are many plugins that aren't updated to 1.8 version yet... so, we can't have a fully 1.8 server until everything is running in the same version...
Yes, you can log in using a 1.8 client, but the "Core" of the server is not 1.8, so no 1.8 characteristics are integrated for now.. they will come, but when is safe and stable to have them.
Don't ask for a due date, they will come when everything is ready... meanwhile, enjoy the experience, there are a lot of custom quests/dungeons/activities to do...