Itโs a combination of three things:
1- most people still google things;
2- the more content you have the more organic traffic youโre likely to attract from Google;
3- displaying ads on your website makes you money.
Websites full of LLM generated content are just the natural continuation of MFAs (Made For AdSense) and there were lots of tools on sale back then in the 2006~2008 period that promised to automatically create websites for you and fill them with randomized content that is optimized for AdSense.