All of those YouTube unboxing videos may have contributed to a greater emphasis on the quality of packaging and the general importance of it.
The boxes keep the resale value higher on used products… which is nice considering how many new products are released every day. People may feel compelled to play with many instruments and gear, but obviously they can’t own them all at once. Maybe they’re just thinking ahead to the day that they may need sell their much loved gear to try something else.
Also, it’s nice to keep the boxes for at least all the gear that feels like an instant classic to you, for the grandkids and beyond to enjoy… or to sell or trade for the latest and greatest if they’re not jiving with the gear of the past, but that’s like… hoarding! Or maybe just highly considerate!