If you look at the keyboards of older devices used with computers (this applies to the United States and Canada only), you will find that the arrangement of characters on them is different from that on the IBM PC.
Some keyboards were "bit-pairing". Those had an arrangement based on the binary coding of ASCII. You could have an arrangement with upper case only that resembled the Model 33 or 35 Teletype, or one with lower case that resembled that of the Model 37 or 38 Teletype.
On these keyboards, ( and ) were over 8 and 9 respectively.
Those arrangements were completely different from that of the current IBM PC keyboard, although there is some resemblance between them and the arrangement of characters on a Japanese keyboard. However, one particular thing is the same: [ and ] are on separate keys, and { and } respectively are their shifts.
Other keyboards were "typewriter-pairing". That meant ( and ) were over 9 and 0 respectively, and the keyboard was laid out much the same as that on a standard electric typewriter. The cent sign, over the 6, was replaced by ^, and you didn't have keys with 1/4 and 1/2 on them.
That was pretty much the arrangement you see today on a personal computer. But with one difference. On typewriter-pairing keyboards, such as those of the LA36 Decwriter, or the Heathkit H8 terminal, ] was the shift of [, and } was the shift of {.
Borrowing the arrangement of those characters from the bit-pairing keyboard does seem to have been an improvement. (It creates a complication for terminals that support APL, though, because then the standard APL-ASCII encodings don't lead to a standard APL keyboard arrangement.)
When did this happen?
My research has led to the VT100 terminal from Digital Equipment Corporation, in 1978, as being at least among the first devices to embody this modified version of the typewriter-pairing ASCII keyboard. I think it, or some other device from DEC released that year, probably did originate the trend to this keyboard style.
It caught on quickly; as I also note on my web page, the HP 300 computer, that came out in 1979, the next year, did this also.
Since this is the place for the keyboard experts, I ask: did someone else inspire DEC, or was there some meeting where the official keyboard layout standard got revised, with DEC perhaps just being the first company to implement it?