It's not automatically 60Hz -- the Apple TV will query your display when it first boots up and asks it what its preferred resolutions and framerates are. Most, but not all, displays sold in PAL countries will tell it 50Hz and the Apple TV will switch to that. For example, I'm in the UK and the Apple TV runs at 50Hz on my Panasonic TV but 60Hz on my Samsung monitor.
We really need to be able to select our own framerates as many people outside the US have material at a range of framerates, and 24fps material doesn't look great at 50Hz. But if you have a lot of 50Hz material the Apple TV may work fine, depending on what kind of TV you have.