Well, not just the Hulkbuster suit, why is Tony even wearing any of the Iron Man suits given that it puts him in danger?
Throughout the movies, remotely controlled suits and drones have always been shown to be inferior in combat performance to worn suits. See e.g. the hammer drones in IM2, the iron legion being destroyed in IM3, the iron legion again in A2...
Rhodey (Iron Man 1): The future of air combat... Is it manned, or unmanned? I'll tell you in my experience, no unmanned aerial vehicle will ever trump a pilot's instinct.
Further, Tony does not appear to prize his own personal safety very greatly, instead valuing the personal touch being Iron Man provides.
Finally, if a remote controlled version of Hulkbuster did exist, it would have fallen into the hands of Ultron.
So, basically, to go up against the Hulk, Tony wants every edge he can get. And he's not worried about getting hurt in the line of duty, otherwise he wouldn't be Iron Man in the first place.