Then why don't you do it? The people who can do it lack interest. As far as piracy goes, a lot of people who develop actual exploits and software are against piracy, believe it or not. As for the specs, they don't matter anymore. Why would somebody get a DSi for hacking? There's WAY better choices (handhelds with WAY more power), and some of these choices have been around since before the DSi existed.
Yes, the DSi is double the speed of the DS. Whoop-de-fucking-do. Celebrating that is like giving the slow kid in class a gold star for effort. A 67mhz ARM9 (the 33mhz ARM7 is delegated to Wifi/Sound/Saving), double that is... still shit. You can probably buy dildos with more processing power than the original DS nowadays, it's 8-year old handheld hardware at this point.
And more RAM? A whopping 16MB? Come on, the original model PSP had double that, and the later models have four times that amount, and they've been available for ages, all of them having 16 times the RAM of the original DS.
And for what, a touchscreen? One 4:3 screen that's single-point resistive, at 256x192? I don't even need to mock this compared to the screens on modern handhelds.
The average phone or mobile coding device is like a hundred times more powerful than the DS, with better touch screens and sound, bigger or smaller form-factor, etc... and a lot of these devices can have custom-code run on them, no hacking needed.
Even as far as gaming handhelds go, you have china-produced modesl like the Dingoo, and the PSP, and the Pandora, and on and on.
EDIT: Pretty much, think of a modern hacker deciding what to buy.
"Well I could buy a DSi with old-ass hardware and 16MB of RAM and spend lots of time developing a custom hack for it... or I could buy a modern android/whatever device with buttons and have eight to twenty times the power and not have to do any hacking of the system itself to get started, I can start coding on day one."
The choice is obvious. The DSi was much too little, much too late.
And this is coming from somebody with a DSi. When I got my PSP I went and deleted all the emulators off my DSi's flash cart.