[Flibble21]

You're missing one of the very important aspects of a RPI is that it's cheap and accessible. Many countries around the world, particularly the poorer ones, don't have Amazon or ready cheap access to SSDs. What they do have access to is phone micro SD cards in adaptors. An 8 or 16GB card is plenty for a computer lab and is affordable and accessible.

[bufferoverflow]

Which country doesn't have access to SSDs?

[culopatin]

They are saying that having an SD port allows people to spend less by using 8-16gb storage cards that are much cheaper than a 128gb M2 SSD. In many countries the RPi is already a big expense on itself and import taxes and low demand often inflate its price even higher. Same happens to other electronics, combined with the reduce buying power, it all adds up really quick.