because bitcoin debit card is not using bitcoin, it is using a third party that holds your bitcoin and may or may not allow you to use your bitcoin and may block your account, run away and scam you, and also it takes a lot of additional fees from you just to let you use your bitcoins!

in comparison the device that OP wants, puts you in full control of your money (your bitcoins). you can spend them however you like and whenever you like and never pay any additional fees apart from miner (network) fee.