I believe that most, if not all, cell phone cameras have cheaper CMOS sensors, not CCD sensors (which have a lower image noise, but they need a more expensive manufacturing process, less compatible with modern digital logic and more similar to the manufacturing processes used for DRAM).
AFAIK the CCD technology continues to be used only in large-area expensive sensors inside some professional video cameras, in applications like astronomy, microscopy, medical imaging and so on.
Quite true even full-frame DSLRs typically use CMOS sensors for some time now.
CCD was the first thing that came to mind as 'charge' is right in the name.
Out of curiosity, looked up invention dates for CCD 1969 and CMOS 1963 and CMOS sensor 1993 (quite a gap). I was playing with DRAM light sensitivity in the lab in the late 80's. I'm guessing CMOS had too much noise to be useful for a long while or something.
No, it was not taken as a given, it was an example of a very common product that digital image sensors enabled. I could have chosen e.g. digital cinema cameras, but they would not nearly have the same profound effect as cell phone cameras have had on society.
