The simplest: Predict what features a user is most interested in, drive them to that page (increasing their predicted conversion rate) -> purchases that occur now that would not have occurred before.
Similarly: Predict products a user is likely to purchase given they made a different purchase. The user may not have seen these incremental products. For example, users buys orange couch, show them brown pillows.
Like above, the same actually works for entirely unrelated product views. If users views x,y,z products we can predict they will be interested in product w and we can advertise it.
Or we predict a user was very likely to have made a purchase, but hasn’t yet. Then we can take action to advertise to them (or not advertise to them).