Facebook, Instagram, and Twitter all used to use chronological feeds instead of ones sorted by personalized algorithms. They switched to the latter because they

Facebook, Instagram, and Twitter all used to use chronological feeds instead of ones sorted by personalized algorithms. They switched to the latter because they found they could make the platforms more addictive and increase screen time and therefore ad revenue. Doing so also involved them making the algorithms purposefully seek out inflammatory content in many cases to show to users because that keeps the user on the platform longer.