Why the obsession with storing everything to SD card?

There appears to be widespread obsession with storing everything possible on a phone's SD card. I've read Android (I have 8.1 Oreo) uses an SD card formatted "internal" not "portable" the same as the factory-built internal memory. What difference does it make if the non-removable factory-built "internal memory" fills up? Supposedly, it doesn't make any difference to Android.

from Android Forums at AndroidCentral.com - Ask a Question http://bit.ly/2GKRi7i
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