Imagine you read one comment in some forum, posted in a long conversation thread. It wouldn’t be obvious what’s going on unless you read more of the thread right?
A single paper is like a single comment, in a thread that goes on for years and years.
For example, why don’t papers explain what tokens/vectors/embedding layers are? Well, they did already, except that comment in the thread came 2013 with the word2vec paper!
You might think wth? To keep up with this some one would have to spend a huge part of their time just reading papers. So yeah that’s kind of what researchers do.
The alternative is to try to find where people have distilled down the important information or summarized it. That’s where books/blogs/youtube etc come in.