Why is this the case? Is there some societal expectation? I know that eg: american grocery stores are much more accepting of returns for any reason vs european ones in general.
There is societal expectation. Frankly no one wants opened/used products, so you know those will be sold at significant discount, or refurbished, or thrown away. No business accepts that unless they HAVE to.
Um ... When I buy for myself I look for open box products all the time. Steep discounts (sometimes 25% or more) are awesome for something that is essentially new. I don't give a shit about the unboxing experience unless it's a gift for someone else.