I have been glancing at the habitat data recorded for each observation and about 10% of observations have no habitat recorded. Have also glanced at who has not put habitat and it seems to be everyone occasionally misses it out, I certainly have done it quite a lot and it just seems to be a mistake rather than deliberately missing it.
If anyone wants to add habitat to their observations where it is not present then I have a list of the observation numbers (i.e. the url) of each one that is missing per person. If you contact me via the inbox then I can send you your listing of missing ones.
As an example here is the beginning of the listing for me, I have fixed the first handfull but not yet done the rest: