If you actually look at the ascii chart broken out by bitfield you’ll see that the codes and key tops reflect a tight mapping (remember old teletypes were electromechanical: an electric motor drove the platen but all the keystroke decoding was mechanical. The usual ascii chart (e.g. man ascii) obscures this by using hex or decimal codes.)

So they had a block of 31 control character (forget null, and delete obviously wasn’t in there because of paper tape).

Many of those control characters were and are useful (^s for stop, ^r for resume) much of the space was empty and so randomly assigned. There would have been room for more bell characters, but that wasn’t really the mentality of the day.