@oldpax
There was a couple I can remember out of the UK from Gatwick on a ski holiday to Europe who had swallowed the line about how you need not have hand baggage and had put all their stuff in their hold baggage.
Gatwick suffered a power failure and all the hold bags were left there at Gatwick.
So they arrived at their destination with pretty well nothing other than what they were wearing plus a small daysack.
Now while you can hire ski boots, helmets and some other stuff, all the things I (being rather wiser) put in my hand baggage such as goggles, sunglasses, face mask, hat, ski gloves, base layer, change of underwear and a single pair of ski socks, toothbrush, electric shaver were all stuck in Gatwick.
When did their hold bags finally turn up at the hotel you ask - after being endlessly promised for the 'next day'?
Wednesday evening - so in effect the entire week's ski holiday was trashed.
I'm sure they leanrt their lesson about how to in future put your essentials and valuables in their hand baggage and cram it right up to the weight/size limit.
...and that is essentially why the concept of hand baggage exists (and that airlines charge for hold baggage)
because the not stupid know that there is a fair possibility of their hold baggage being delayed, lost entirely or of valuables in them going strangely "missing".
As to why they take them when they leave..
This blog might just possibly give a clue:
https://nickbradbury.com/2013/07/28/...southwest-345/
He left his hand baggage behind, it was retrieved later by the airline and returned to him, 2 days later note, and minus the apple mac book pro in it - well what a surprise - who'd have guessed it.
I'll bet he will be grabbing his hand bags next time as well