People can be cutthroat about trying to get their name on papers to which they contributed little, and they may be reluctant to discuss work too openly with oth

People can be cutthroat about trying to get their name on papers to which they contributed little, and they may be reluctant to discuss work too openly with others lest the discussion be construed as a collaboration which would require coauthorship. But I think leaving people off the paper who made some contribution is really frowned upon at least in the US.