Whilst I do think that "Christmas Eve Boxes" have become a commercialised commodity in the modern era of showing off on social media, the spirit of the tradition is a lovely one that goes back many years, it's not just some new fad.
My DD has always had a Christmas eve box following the same tradition of the Christmas eve routine that I, and my siblings, grew up with.
Every Christmas Eve as children our mum would strip the beds first thing Christmas eve morning to put our Christmas bedding on, which would then stay on till Epiphany, and we we would be sent out with dad to go out on a family walk to drop off gifts/cards to anyone we hadn't seen in the previous week and wouldn't be seeing on Christmas Day itself so mum could "get the washing done" and also deal with any last minute wrapping/present collecting from neighbours and other friends and family who had kindly stored things as mum and dad didn't have room to hide four kids worth of stuff . We would then come home, have tea then go to the 5pm Christmas Eve church service with mum (she's Irish Catholic, dad was brought up atheist). When we got home there would be gift bags lined up under the tree with new PJs, slippers and some new shampoo/shower gel/bubble bath for each of us. There would also be the little basket that we would leave out with Santa's mince pie/carrots for the reindeer which would have a new Disney video/DVD and a tin of Christmas chocs.
We'd all open our bags, go up and have a bath/shower, get into our new PJs and slippers and come back down to the living room where mum or dad would have set up the living room ready to watch the new Disney film, with the Christmas chocs and warm cocoa/Horlicks for everyone.
When we were little kids and/or when there was a mix of older and younger siblings there was a Christmas story book added to the basket so instead of staying up for movie night, mum or dad would read the Christmas story book to the little kids and tuck them in to bed while the big kids were getting bathed/showered and going down for movie night.
As we all got older and past the Santa stage we'd still get the gift bag but instead of the book/DVD we'd get a board game instead and we'd have a fun evening of opening our gift bags, having a picky tea of buffet buts mum had bought in the supermarket party section, playing a family board game with Christmas music on and a tin of chocs working it's way round the table and then we'd have the option of whether to go to bed or stay up to accompany mum to Midnight Mass. Whether you stayed up or went to mass, before bed you'd get washed and dressed in your new PJs so you looked at least partly presentable in the 5am photos of all the present opening mum and dad took every Christmas day.
With my DD I continued the same tradition - Christmas Eve church service, home to the Christmas eve basket with PJs, slippers, a Christmas story book, a new DVD and a cup of chocolate and churros (when we lived in Spain)/cocoa and christmas cookies (when we moved back to England).
As DD is an only child the only change I made was to give DD her Christmas Eve bag on the morning of the 24th and I'd add a few little craft activities, a small toy, sticker/colouring books etc to the box so that I could keep her occupied through the day if I needed to get any last minute prep jobs done. When we lived abroad and travelled back to England for Christmas we'd often be in a hotel (I preferred having our own base to retreat to if things got too much with the whole family celebration and I am not a fan of sleeping on camp beds/sofas unless absolutely necessary) so giving DD the bag on Christmas eve morning meant I could have a few extra minutes in bed and/or gave myself a bit of time to get organised.