User blog comment:The Xoudian/AN URGENT MESSAGE TO ALL ADC MAINS/@comment-5266525-20150605155652

The issue is less that they don't know the lantern will save them and more they either don't expect it or don't notice it when trying to get away.

It's a two-way street as well, Thresh players can be to blame for poor lantern placement. Throwing a lantern directly at them when they already have 6-stack Cho'Gath standing in their face isn't likely to result in much success.