Put your tin hats on...
I think iRex used these type of buttons just because they could. In old iLiad there is also a lot of strange hardware (audio, two different memory card slots, USB connection that never worked, standard ethernet through dock), probably somebody with strong engineering background and no marketing vision for the device decided to stuff all that into iLiad following more is better... Now probably someone who knew about capacitive sensor thought they are such a neat piece of electronics and stuffed those into DR without thinking more than 3 seconds about usability. Sorry, but iRex guys in my opinion have strong management/product development issues... I personally use my old worn iLiad and wait for next year to see if iRex manages to deliver any of the promises it has made for the DR.