Why to develop a new technology instead of reusing the existing one?

Many useless blockchains still retain their value because they were first or managed to promise they are not useless.

In order to enter the market - and we are aiming at the payment processing business - we should enter through closed loop systems first (loyalty rewards, gift cards, promotion coupons, store credits) because it is much easier than open loop payments which involve direct operations with fiat. For that purpose we have to have a particular set of key features: ability to create multiple merchant and consumer tokens, high scalability, instant authorizations and settlements, zero fees for some transaction types, very light clients, no locked balances, no chargebacks.

Let's face it - we are far away from this set with PoW blockchains which will not allow us to enter the market, at least not fast enough because there are much more features required that will take years to implement on CryptoNote (like tokens) or simply impossible to do on PoW (high scalability, zero fees, unlocked balances).

See also: Is it better to build your own rather than building on the backs of giants?