People who have careers in tech are likely to read an internet forum whose readership is directed at people who have careers in tech. So we aren't going to get much "people who don't have careers in tech" side of the story.

Hypothetical example: Say only 1% of coding bootcamp graduates find the program to be a "success" for them. All of that 1% read hacker news and zero of the 99% read hacker news. If you ask about bootcamp on hacker news you'll only get HN reader's perspective, then you'd believe bootcamps are wildly successful whereas the real number is the opposite.