Scrapers nowadays can use residential and mobile IPs, so banning by IP, even if actual malicious requests are coming from them, can also prevent actual unrelated people from accessing your service.
Anyone who owns a chrome extension with 50k+ installs is regularly asked to sell it to people (myself included). The people who buy the extensions try to monetize them any way they can, like proxying traffic for malicious scrapers / attacks.
Also a lot of big companies are paying for residential "proxies" to scrape traffic from for AI.