If you don't care about how science street cred works, nothing stops you from just throwing your papers up on arxiv. But then you get no publishing rep. And no visibility either. A big name journal in a given field gets eyes on your paper by default, but in the pits of arxiv, if you don't put your work out there yourself in the circles, no one will see it.

There are a lot of researchers writing papers. In many fields it isn't possible to read them all, so you need someone to make a selection of what is useful. Get into Nature any "everyone" will read your paper because it is important. However if you fail that you only get into a small niche publication - the only people who will read your paper are people who search it out - likely because they are in that tiny niche (and have personally met you to discuss this niche at a conference). There are even lower grades up publications which nobody reads, but in theory someone could find it in a search.

What physics papers should a chemist read? If you are a physicist you should be reading more papers, but there are still too many to read them all so you need a selection, but that selection should bias to others working on similar problems to you. The same applies for every other field: you can't know everything so you need someone to apply a selection to tell you what is important for you to know.

1. https://www.bbc.com/news/uk-england-hampshire-11964995