I think it's also pushing subscription based cloud services. To me, the SD card slot is a convenient backup target when away from home. It fits my 3-2-1 backup strategy. Without it, more people will consider backing up to paid cloud services, like how Apple does it.
For the record, I hate this trend. Hands off my sd slot and my 3.5mm jack. But I also want GrapheneOS or something similar. Can't have it all...
If there is no expandable storage, you have to buy the 2x expensive phone with more internal storage. That's the game they are playing.
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