Purse.io is great in a bull market (basically taking profits when you spend), but punishing in a bear market when you want to HODL. 15% discount doesn't matter if you're 20% down this week.
If you buy BCH and immediately spend it on Purse it is still a good deal in a bear market. Also, it's better to spend your BCH on Purse and get 15-20% extra than cashing out to fiat.