Coupons are really not attractive anymore.
Most sellers deliberately list the item prices at a few cents below the minimum spending for coupons just to avoid it eg. $3 off min spend $20 and they sell the item at $19.90.
Why do they deliberately do that? You know sellers doesn't absorb the costs of your voucher? Like if you paid $17 off a $20 item they still get $20-their commission fee Qoo10 charges.