Terminal input, shells and so on were all rudimentary by modern standards in v6. By v7 things had become more familiar to 21st century folks. But for v6, although it was an advancement on many systems extant at the time (although not all), the clunky nature of this generated a vast flurry of hackery around terminal drivers and shells. It's a messy history.
For the record, our v5/v6 lab in Toronto had mostly paper terminals, despite being a graphics lab, and one of them, the DECWriter, didn't even have lower case. Be thankful for your current setup.
One example of the limitations: in v6 you could not pipe into a shell script because the shell used the script itself as standard input. And the argument list was limited to 512 bytes.*
But hey, in v1 there weren't even multipart path names.
-rob
* My first day at Google using Linux in 2002, I got "arg list too long" with a modest glob pattern, and thought, what, have we forgotten about dynamic memory allocation? Moving to a Unix system after a decade plus on Plan 9 was a shock.