It's way easier to have a centralized system than decentralized one. Bitcoin in it' current form can handle around 7 transactions per seconds, and scaling it upwards is costly. 7 transcations per seconds is laughably small number. Your smartphone using LTE connection could serve 7 transcations per seconds as trusted centralized server.
I'm not sure where you're getting the 7 TPS number. Satoshidice alone is responsible for more than that. It's trivial for anyone to send hundreds of transactions per second if you're willing to pay the miner fees.
