And for the vast majority of use cases, even if QLC wears out TLC would be fine indefinitely. Limiting it to SLC capacity would be ridiculous.

I have USB drives with good old SLC flash, whose data is still intact after several decades (rated for retention of 10 years at 55C after 100K cycles - and they have not been cycled anywhere near that much.)

and consumers would rather have more storage

No one from the manufacturers tells them that the "more storage" - multiplicatively more - lasts exponentially less.

For the same price, would you rather have a 1TB drive that will retain data for 10 years after having written 100PB, or a 4TB one that will only hold that data for 3 months after having written 2PB?

That requires support software they may not want to build

The software is already there if you know where to look.

and support requests from users complaining that toggling SLC mode lost all the data or toggling QLC mode back on did similarly

Do they also get support requests from users complaining that they lost all data after reformatting the drive?

It’s a valid business decision to not support that kind of product feature.

The only "valid business decision" is to make things that don't last as long, so recurring revenue is guaranteed.

Finally, the "smoking gun" of planned obsolescence: SLC flash requires nowhere near as much ECC and thus controller/firmware complexity as MLC/TLC/QLC. It is also naturally faster. The NRE costs of controllers supporting SLC flash is a fraction of those for >1 bit per cell flash. QLC in particular, according to one datasheet I could find, requires ECC that can handle a bit error rate of 1E-2. One in a hundred bits read will be incorrect in normal operation of a QLC storage device. That's how idiotic it is --- they're operating at the very limits of error correction, just so they can have a measly 4x capacity increase over SLC which is nearly perfect and needs very minimal ECC. All this energy and resource usage dedicated to making things more complex and shorter-lasting can't be considered anything other than planned obsolescence.

Contrast this with SmartMedia, the original NAND flash memory card format, rated for 100K-1M cycles, using ECC that only needs to correct at most 1 bit in 2048, and with such high endurance that it doesn't even need wear leveling.

Also consider that SLC drives should cost a little less than 4x the price of QLC ones of the same capacity, given the lower costs of developing controllers and firmware, and the same price of NAND die, yet those rare SLC drives which are sold cost much more --- they're trying to price them out of reach of most people, given how much better they actually are.

Used LTO5+ drives are incredibly cheap, you can get a whole tape library with two drives and many tape slots for under 1k.

Tapes are also way more reliable than hard drives.

HDDs are a pragmatic choice for “backup” or offline storage. You’ll still need to power them up, just for testing, and also so the “grease” liquefies and they don’t stick.

Up through 2019 or so, I was relying on BD-XL discs, sized at 100GB each. The drives that created them could also write out M-DISC archival media, which was fearsomely expensive as a home user, but could make sense to a small business.

100GB, spread over one or more discs, was plenty of capacity to save the critical data, if I were judiciously excluding disposable stuff, such as ripped CD audio.

> But this is only good if you have single digit of TBs or low double digit of TBs

That's not so enticing when I could get 3 16TB hard drives for half the price, with a full copy on each drive plus some par3 files in case of bad sectors.

I have used LTO5 drives under FreeBSD and Linux. Under Linux I used both LTFS and tar. There was zero issues with software.