The 20 years thing was my bafflement as to why people felt the need to explain what Captchas are. Not a justification for their existence. When I ask "why" I think I'm pretty clearly not asking to have how Captchas work explained to me.
Putting that aside, can you explain to me how asking you to identify a traffic light is "at the expense of literally everyone"?
Someone was saying "they'll train smart cars! And sell it to us as a subscription!" which I think is the same route you're going down. But... how is that at the expense of everyone? And would not training smart cars benefit anyone? Is someone else going to do it? Is there a FOSS smart car I can contribue to? And is that FOSS going to prevent bad actors from training it to misbehave?
I'm almost certainly older than you, but I'm still interested to hear how deliberately answering Captchas incorrectly saves time over answering them correctly.