Security: Newer browsers protect you better against viruses, scams and other threats. Outdated browsers are slow and have security holes.
Speed: Every new browser generation improves speed. Even minor updates can make a considerable difference to speed factors.
Technological compatibility: Modern websites are taking advantages of all the new features that modern web browsers provide.
Better experience: Have a more comfortable experience with new features, extensions and better customizability.
Why this website asks to update your browser?
This is an initiative by websites and blogs to raise security awareness and bring forward the web. Find out more about this on: browser-update.org or whatbrowser.org or outdatedbrowser.com.