Cash is common in China...or now a days, on WeChat you can send a "Red packet" of money to friends or in a groups. If you go to a wedding, you drop your red packet in a box...while in the US we have "gift registries" where a newly wed are forced to acquire physical possessions they may or may not need.

I'm not sure why cash is taboo in US - I suspect it's derived from corporations trying to drive customers to purchase items, even gift cards. After all, $1 saved is $1 not spent and that's bad for profits /s.