When you look at the list of currencies, there are categories. One of them was for Season 1. Anything under that category is removed upon new patch when the season ends. That’s why it’s under a season category.
We were also told this:
And I’m sorry, but I’m just getting tired of people blaming Blizzard when we’ve had several articles, and previous seasons of this happening, along with blue posts and people talking about the season 1 currencies going away.
No little square of news in game is going to change anything. People ignore pop ups, news bits, tooltips, all of it.