Yep, its easy for DMs to get in the mindset of "challenging" the players. But sometimes the players really do just want to show off and kick butt.Have more interactions and/or combats against lower CR creatures.
In my first campaign, the players got "house arrest" and had to stay in the city because of some issues. Aka they couldn't go adventuring. So they decided to enjoy their "vacation" and help out around the city. These 11th level characters took down a low level smuggling ring in an hour, just knocking heads and completely dominating everyone they encountered. The players had a blast, they still talk about it 9 campaigns later.