Never? How can you say that? Yes, they do try to get people to gate check bags before they board. But I can say many, maybe most, of our flights have last minute gate checking of at least a couple bags, because the overheads get full.
United is installing slightly different overhead storage bins on their single aisle planes (think they have started with the new 737 Max models) that have 15-20% more space in them. They even have a training video they show at the gate how to properly store your bags in them to achieve more efficient use of the space, and it works surprisingly well.