It's not routine. Most tourist visitors don't have any trouble. I'm a US citizen, but I've never had my phone searched at an airport or border crossing, not that I cross the border all that often.

I know it isn't routine. But it does happen. I know two people that had to go into secondary inspection and I think they had to unlock their phones. Both of them were completely normal business travelers without anything dubious in their life or their business. One was a medical doctor another one a government employee going to an international conference hosted by a US federal institution (which required some extensive clearance and background checks to even attend). Both Western European citizens with a completely spotless CV.