It is a very basic SDK right now, it is still in development and has a long way to go. Considering the exploit to run code only works on FW 1.76 (~1 year old), there presumably aren't many people able to run code anyway.
[1] http://wololo.net/2014/10/24/webkit-exploit-confirmed-to-run...
It sure is, also a bit sad that it takes such detours to be able to write software for such devices. Years ago when the first PSP came out things were different. I bought the PSP just because I saw there was a rather complete SDK available for it (also made available by hacking around and reverse engineering IIRC, but at least it was more than enough to write actual applications): it included access to buttons, sockets/wifi, raw framebuffer access etc. Which led to the availability of fun things like a working VNC client which was super impressive to me back then (remember that's like 5 years before the first iPad). I had only like one game which I never really played but instead I spent hours writing mini games and setting up communication between the PSP and a PC, using it as remote control and whatnot.
And that's exactly why manufacturers go to such lengths to prevent people from hacking on their consoles. With the way they are priced, and depending on when you bought that PSP, it may have cost Sony money if you didn't buy any games for it.
1.https://en.wikipedia.org/wiki/PlayStation_Mobile
2.https://en.wikipedia.org/wiki/Linux_for_PlayStation_2
There is this revolutionary business idea of selling stuff at profit. Cross subsidizing always bites you in the ass. Loss leaders too.
As for the sparseness, definitely true, the SDK really doesn't have much in the way of functionality yet, but I'm kind of surprised by what they have so far.
Kinda feels like it's a little short for a SDK too, but I'm no expert.