HDD cost small dollars only for small amounts of archived data, i.e. up to 100 TB or 200 TB at most.

For greater amounts of data, HDDs become too expensive and this is the main reason to switch to tapes.

Obviously, for someone who is certain of never needing more than a few tens of TB of storage space it would be foolish to use LTO.

On the other hand, for someone storing 500 TB, it is foolish to use HDDs, because tapes are more reliable, more compact, faster for sequential transfers, i.e. the actual backup and restoring, and cheaper.

It is as simple as that. The decision of using HDDs or LTO is strictly determined by the amount of data that must be stored.

The argument that HDDs should be fine for most non-technical people is correct only because those people do not store much data.