As one of the belittled Movs family, I will put in my £0.02.
I am responsible for the PAX and the load of the ac and the presentation of that 'safe' load to the ac crew. If you are carrying something that might just go bang, spark, whoosh, corrode etc it is up to Movs to make that safe.
We just apply the rules provided.
Oh - and yes - I have seen some supposedly educated people carrying some really stupid & dangerous things on board. Sometimes a genuine mistake, but often a complete disregard for safety and a lack of understanding.
And no - carry your own fekkin bags!