[blokey]

Because APFS is slllloooowowwwwwww on HDDs. On a 6xHDD promise thunderbolt array, it’s brutally crippling over time.

One reason is APFS is designed for SSDs and assumes each disk block has an equal latency to read it.

[neuronexmachina]

I think Apple hasn't sold anything with an HDD for 5+ years though?

[coldtea]

Billions of externals HDD exist, continue to be sold, and are the best price/performance/durability for external backup drives though?

[adrian_b]

As another poster already noted, external HDDs may be needed, especially because Apple computers have only puny (or greatly overpriced) SSDs.

[a96]

Usually both at the same time. Soldered on the board and unchangeable.

[ChocolateGod]

External HDDs.