Because it is there.
From an interview, ('Climbing Mount Everest is work for Supermen', New York Times, 18th March 1923) on being asked why he wanted to climb Mount Everest:
One comes to bless the absolute bareness, feeling that here is a pure beauty of form, a kind of ultimate harmony.George Mallory
I look back on tremendous efforts & exhaustion & dismal looking out of a tent door on to a dismal world of snow and vanishing hopes - & yet, & yet, & yet there have been a good many things to see the other side.George Mallory
Gradually, very gradually, we saw the great mountain sides and glaciers and aretes, now one fragment and now another through the floating rifts, until far higher in the sky than imagination had dared to suggest the white summit of Everest appeared.George Mallory
"Why do we travel to remote locations? To prove our adventurous spirit or to tell stories about incredible things? We do it to be alone amongst friends and to find ourselves in a land without man."George Mallory