Promo Items
Because it’s a limited-time offering that’s not be seen for some time.
Some of the ‘promo’ promotional items are widely popular, some less so. Some haven’t been seen for years, some for only weeks.
Think promotional as being either new, returning, special offer, or at a discount.
“Promotional” need not include a discount. It just means that it’s being highlighted. Probably the more accurate phrase is “promotional discount”, but over time, the difference has become less distinct.
John Smith: “you should kill monsters, because killing monsters is awesome.”