Why lowercase [i] does not work in visual block mode?

Question

I often forget how to insert in visual block mode and read again the answer Shift+i.

As Honghe.Wu wonders in his comment:

Why lowercase i

Answer 1

The i command inserts before the cursor position. In visual block mode, the cursor position (usually) represents the bottom right corner of the selection, and the cursor position is included in the block.

So, the semantics of i wouldn't match, and that's why it was left out of the Vim implementation (adding that would probably be a simple one-line change to the source code). The semantics do match for I (insert before any text) and A (insert after any text), that's why those are available in visual block mode.