And optical media is also immutable (read only) when you need it to be immune to any data changes.
I find that read only point in time backups gain value over time. Especially if you need to pull a file that would have been long rotated and replaced by newer backups on read write media (eg. HDDs).
Unfortunately the market for this use case is not large and this is greatly reflected in the prices and relatively hard to source high quality optical media. For BD this would be (inorganic) HTL Panasonic media which only has a market inside Japan itself. M-Disc is the other alternative although it only has proven itself within the DVD market, as classical HTL BD media is expected to be very similar in endurance to what M-Disc has on offer in the BD range.
( * ) So you don't need a power adapter.