When I stayed at the HGI on the south Las Vegas strip earlier this year they asked for the card at check-in. As a Diamond I gently reminded the guy about Hilton policy allowing me to just have them use the card in my profile. He was nice but told me that due to fraud issues in the Las Vegas area they had received a special waiver from Hilton and could require all guests to present their card at check-in. I went along (partly because I was very tired and just wanted to get to the room) but did mention the issue in the post-stay survey I received. As a result of the survey a manager at the hotel emailed me and confirmed what the front desk agent had told me.

Long story short: Apparently some hotels can get permission from Hilton to require the physical card at check-in even for Golds and Diamonds.