I suspect because they werent even thinking of cyclists as a particular use case to test on the trains, for instance they regularly quote theres space for 6 bikes on these trains, but from the space Ive seen you could probably only fit maybe 4 at most, before blocking the aisle to other passengers, and probably 2 at most if they are carrying panniers/luggage, plus you have to play bike jenga to get the things in/out assuming no-one has decided to stand there, dump their luggage/pushchairs there.so actually I suspect on the 755s at least people will just park up in the doorways like they do on the Overground in london or on EMUs which may or may not cause more problems for other passengers, but thats about the best theyll be able to do on the Sudbury service unless they extend the platform.
presumably they got the length right at Sherringham ?