I'll go through some personal upsides to using eww.

The main utility I see in browsing the web through emacs is the potential to integrate it into your workflow. You can have your code/notes open in one buffer and have the website in another, which is useful for documentation, or an article you're following along, etc.

With gptel, it's easy to highlight part of a blogpost and ask an llm a question about it, or get it to rewrite or annotate the whole page.

With macros you can do basic automation, like this webscraping example here: https://nickdrozd.github.io/2018/10/17/web-scraping.html

An added bonus is that your keybindings for the rest of emacs are also valid here. (Though for that I've recently started using Glide, a firefox fork, and set all of its keymap to match my emacs bindings)