Another thing to consider is payment
Pre-orders give you the option to pay beforehand
But in most situations you pay when you buy. In the modern world people can accept card payments in a field - if they have their card machine and a phone connection, cash is king though
Once upon a time many years ago a trader was accepting card payments with no working machine - they took your details and charged it the next day when back at the shop
Quite a bit of trust there, and it was not just to event regulars, it was in my early days and I know I walked off as a stranger with a potentially free electric hopper in my hand
(It was an apache 2k - which I remember very well as my VL Revolution had its lid shot off while reloading and they didn't have spare lids, so I bought a new hopper - and subsequently ordered a lid later on)