I'm American and use credit cards for everything, and I know what you mean. I almost never have to sign receipts anywhere as long as my transaction is low enough. Usually the only time I'm signing receipts or screens is if it's a bar or restaurant with tips.
When this first started happening I asked one of the workers at whatever store I was in and they said it didn't require signatures under a certain transaction dollar amount. IDK if laws in the US changed or what around that time, but it seemed to suddenly change everywhere.