No, the real reason is that upper case was customary for telegrams and then teletypes. Upper case was well established before CRT displays came into play.
All have characteristics that set them apart from potential lookalikes - the bar through the 0 is one excellent example - but it’s up to the font designers to take readability into account, and most designers are looking at reading English prose, not code. They don’t think “my font might be used to render a URL in a context where a user will need to make an essential security decision based on whether the string they’re reading contains an l or an I.
`if`, `then`, `else`, `while`, `return`
vs `goto`, `comefrom`
... Well, it's arguably superficially a better argument than Dijkstra's, but it doesn't account for `for`, so I'm not convinced.