On the other hand, I have found that most of the time the "I don't care, it works for me" people are just lazy or incompetent. Others mentioned blocking your site for screenreaders and ethical scrapers, I can add non standard (mobile) browsers to the list.
You might say you don't care about them. I say that is the same as throwing your household waste over the fence and let others fix it. It doesn't exist if you can't see it! The web as a whole becomes more inaccessible, it fortifies existing monopolies and mono culture.
It does not have to be perfect, you don't have to spend days. A little effort and awareness goes a long way.
H1 for main page heading h2's for sub headings and <tables for tabular data eg a list of ingredients or technical data
One use I have seen for table of the basic details of a yacht, displacement, speed , length etc
This is your perception, but if you don't use semantic HTML, you are building elements that look like something (for sighted users) but in reality, is something else (for assistive technologies and search engines).
So, it only works for a part of your users. And maybe it works for the majority of your users, but that means that you are making it hard for people that use assistive technologies and search engines to navigate your site.
Leave alone people with disabilities because you don't seem to care. Search engines need semantic HTML to crawl correctly your website, so it's an important part of any project.
It’s also interesting because certainly you must have come across those engineers and developers who’re so well versed in their particular portion of the field that they know to tweak VM settings for memory leaks, or how to shard databases for faster queries, or why your Z-index isn’t working.
Those people most likely spent time studying their crafts and learning the “correct way” to do things.
Just a dick move.