Why are breakpoints caught by the runtime?

[via Digitalmars-d]

On Sunday, 15 June 2014 at 14:50:30 UTC, Trass3r wrote:
> void main()
> {
> 	asm { int 3; }
> }
>
> object.Error: Breakpoint
> ----------------
> 0x00402013 in _Dmain at bptest.d(6)
> 0x00402314 in void rt.dmain2._d_run_main(int, char**, extern 
> (C) int function(char[][])*).runAll().void __lambda1()
> 0x004022E7 in void rt.dmain2._d_run_main(int, char**, extern 
> (C) int function(char[][])*).runAll()
> 0x00402200 in _d_run_main
>
>
> Is there any good reason to catch that?
> I really want the debugger to fire up.

Which OS and compiler version is that? The breakpoint is 
correctly triggered here on openSUSE 13.1 x86_64 / DMD 2.066 git:

     # ./bptest
     Trace/breakpoint trap
     # gdb ./bptest
     ...
     (gdb) run
     Program received signal SIGTRAP, Trace/breakpoint trap.
     0x000000000041b7b5 in D main ()
     (gdb)