Those bad boys (9-track tapes) could easily hold 40MB which was a few hundred times bigger than floppy discs of the 8-bit age and would add up to quite a few compact cassettes. (As expensive as it was, I was so happy to switch to floppy disk for my TRS-80 Color Computer because restoring stuff I saved on a cassette was always hit or miss.)

Mainframes in 1968 were handling much bigger data sets than you could handle with a micro until 1990 or so.