Cold tier cloud storage absolutely has tape behind it. You can even send tapes to some cloud vendors.
Broadcasting is another giant customer. Companies like WBD have Exabytes or Zettabytes of digitized programming (movies, series, documentaries) which would be impractical to store on disk. The typical workflow is for the program scheduler to direct the robot to fetch the tape containing a program 24 hours in advance of the broadcast time and copy it to disk, then erasing the disk copy after broadcast.
I don't think hard drive based storage and tape bases storage have quite the same use case.
An 18TB tape is basically the same size as an 18TB 3.5" hard drive.
I am using older LTO-7 cartridges, with a raw capacity of 6 TB. The newer LTO cartridges must be compatible mechanically with the old cartridges, because the same drive must be able to read and write them.
The LTO cartridges are smaller than 3.5" drives, they have maybe about 2/3 of the volume of a 3.5" HDD.
Moreover, a tape cartridge is many times lighter than a HDD. I have suitcases with 20 tape cartridges that are as convenient to carry as any typical suitcase.
A luggage carrying 20 HDDs would have a very noticeable weight, and its volume would be great not only due to the bigger HDDs, but it would require serious padding to avoid HDD destruction if the case were dropped accidentally.
* https://tapeandmedia.com/lto-ultrium-9-tapes/
If your data is compressible then you can of course store more. The drives themselves use Streaming Lossless Data Compression, but of course you can send them things like gzip, JPEG, MPEG files which are already compressed; SLDC:
* https://www.ecma-international.org/wp-content/uploads/ECMA-3...
LTO-10 is supposed to have 36TB raw and is estimated for perhaps 2024.
However, even those rarely accessed records often have more accesses per year than the hard drives can support - so you are forced to buy 400 drives instead of 200 drives and keep each half full.
End result: There is a lot of 'almost free' space on the hard drives, as long as you are happy to only read/write the data very rarely.