The trouble with doing this, is that it would potentially be a breaking change to an extension. Extensions with bits enabled can only be installed by broadcasters that are affiliates or partners, so if Twitch were to allow this, it would mean that extensions could update and just break/stop working for broadcasters who aren’t a partner or affiliate.
Also, not all partners/affiliates want to use bits enabled extensions running on their channel, to allow this would mean that broadcasters who have chosen to only use extensions that don’t use bits, could suddenly have an update that forces these features on to them and not all extensions will have a way to disable that without completely removing the extension.