I think because they are really part and parcel.
Over the years more and more of these small things have been added, at the same time more and more is spent of gifts in general. People have always had hot chocolate and candy, or maybe a dvd (though in the past we watched tv Christmas specials.)
But the box has been created as a way to package that into a vehicle for selling things. The elf on the shelf is similar, it's basically a version of make up a story to go with the plastic toy you want to sell in massive numbers
I was going to say the same thing.
There's loads of ways to have nice family traditions, so why does there need to be a box, often personalised one per child, why do kids need new Christmas themed pyjamas the night before Christmas when they're inevitably going to grow out of them, single use items, hot chocolate 'kits' and a new mug each year?
A few years ago I read about the waste that goes into the Christmas jumper days and that falls into the same category as christmas eve boxes for me. Some people will have a festive jumper they wear each year, but most buy a new one each year, only to discard it once the photos have been taken, and buy a new one in 12 months time
If someone started a thread asking what people thought about the ridiculous pressure to buy buy buy at Christmas then there would be people sharing their views on that. The only difference is that whilst some people on this thread insist that being cynical at yet another thing that requires more stuff, on those threads you'd inevitably get people claiming that any hint of concern about endless buying is obviously pure jealousy from people turning green with envy over someone else buying a new phone every year/designer gear. 🤷♀️