Hello
Delph and welcome to the forum, sorry not to have replied earlier but we had some trouble in the 'cabin' but your enquiry is now cleared for take off.
You will see that, when mentioning another poster, it is etiquette to put their name in bold, using the buttons above the edit text box.
The weight in the cabin is not so much about 'weight and balance' as the airlines have a very clear idea of how much stuff is where. It is the concern that too much stuff in the cabin will cause a problem in an emergency. If a bag trips up someone making for the emergency exit? Whilst some airline rules may seem curious/strange, you can always decided not to use that airline.
I'm sure that more folks will be along shortly to give more detail.