It is painful. But, it is Turing. Sorry, there isn't any logical explanation I can offer. I tried removing all of the predefs and compiling a simple program (that is, a single commented line) and it did nothing to lower the size noticeably.
The reason, to the best of my knowledge, is that the Turing "compiler" doesn't selectively pick and choose what parts of the Turing standard library to compile -- it just throws it all in. That's why you never need an import line or anything when you're using Net.Connect or Pic.ScreenLoad -- Net and Pic and every other module in the library simply gets compiled in regardless of whether you need it or not. So that's the reason why your "Hello World" one line program is like 300 Kb. It's because Turing can't tell that it doesn't need every single piece of the library.