Why are bolts of brake discs using Torx sockets? Most bolts on bikes are using hex sockets. However, there is at least one exception: the 6 bolts of brake discs, which usually have Torx sockets.

What is the reason for this? Has the Torx socket a significant importance in this area in particular?

Related question: I'm considering replacing these bolts with titanium version (saves 6 grams per wheel, woohoo!), and I can buy them with either hex or Torx sockets (hex would be a bit more convenient as I have hex keys readily available everywhere, on the other hand, the Torx socket is technically better). Can I just pick the socket I prefer, or would you strongly advise for Torx?
The magic of lobes allows Torx to handle a given torque value with a shorter bolt head than the alternatives, and some frame/fork designs need the clearance in this area. That's the only reason for it.

Some secondary bolt retention designs won't work with just any bolts, ie Shimano.