All isn't an appropriate descriptor. If there was money for it in 1970, you could get whatever size companies like IBM had the technology to build.
If you're talking about what's commonly available, hard drives weren't commonly available at all for home/hobbyist computing kits before the 5150, which didn't even ship at launch with a hard drive, despite it being a high end business-oriented machine. If you really needed to store data on your local computer on a hard disk, for some reason, you could get whatever size you could afford, pretty much. As was previously said, mainframe machines definitely had over 10MB drives available in the late 70's.
When the IBM PC/XT came out, it shipped with a 10MB MFM hard disk, with drive sizes increasing throughout the 1980's, but even until PCs really entered into the home in the late 80's, I'd imagine you'd still find people with their C64s, Atari 400/800s, or even Amiga/STs without any sort of hard disk storage whatsoever.
Hard drives initially made sense for random access storage that was cheaper than just a load of ferrite core memory in a box, but not something like a tape drive, which has issues with getting to a specific bit of data in a fast time (which might be important if you're a bank doing transactions).
So home use really didn't need hard disks until prices dropped significantly, and floppy disks weren't enough to store most/all of what you did on a computer.