That's gotta be a European thing. In the US, cassette drives were pretty much non-existent (in favor of 5.25" floppy drives) from at least the mid-80's onward, at least. I personally have absolutely no memory whatsoever of ever seeing anyone actually use a cassette drive to load programs on a computer. (though I did read about it in books on occasion). And I was a kid during the era of the Apple IIe's popularity, with machines of its ilk being my first exposure to computers.

Even into the 386/486 era, at least before CD-ROM drives were commonplace, it was common for computers to have both 5.25" and 3.5" drives and to find software in either format.

It's pedantry and missing your point about progression to 3.5", but given this is wallowing in retro - you can't forget that the ZX Spectrum went to Microdrive and then, with the Spectrum+3, to the 3" (not 3.5") floppy :)

https://www.sintech-shop.co.uk/zx-microdrive/a-3035/

https://www.dataserve-retro.co.uk/contents/en-uk/d56.html

Same here, Commodore V20 cassette & cartridge to Tandy 1000TL/2 3.5” single density.