Since when? I'm not even that old, and I've heard most of my life that 18% means "you did a stellar job" and 10% was "not great, not terrible."
I've always tried to tip 20% minimum anyway to support my fellow humans, usually closer to 25-30% especially on smaller bills, but these days it's frustrating because it almost takes away any of the joy of tipping extra well when it's already on there as a suggestion.
These days I'm all about getting rid of it and just paying a living wage and making the prices match reality.
I've read at least one article suggesting that Square and Clover et al are kind of exacerbating the problem by letting/encouraging business owners to make default tips higher. And I'm sure it's pretty obvious that owners are not super inclined to increase base pay when they can bump suggested tips and pass that cost onto the customer without making things look more expensive.