That would be my guess, they know he did it but cannot prove it to the court.
The suspended sentence though does mean that if he's caught doing anything illegal in the near future he's probably going to prison, and that is probably a much harsher penalty than losing his licence (which in itself doesn't necessarily mean someone is going to behave).
Add to that the 200 hours of community service and he's probably been inconvenienced more than if he'd got a ban for a few months.
IIRC there was a case local to me where someone was deliberately speeding past the camera on his bike with the number obscured/not visible and they had some fun tracking him down - they ended up checking where every bike of the type used was registered, and then compared that to the leathers/helmet and the location of the suspected speeder on the date(s) in question.
From what I remember they only got that one because there were only a handful of bikes of the type around at the time.
I can imagine in this case if he had different bikes at different times and sold them on fairly quickly they probably couldn't tie him down 100% to the bikes at the time of the offences.
