"why not?" - simply because your procedure/application will not be suitable with global methods like Ethereum or Bitcoin where by ensuring uniqueness of addresses on a worldwide scale would be the a major objective. This can be the question you need to be inquiring - (ethereum.stackexchange.com/inquiries/3542/�? Would you double-Check out https://marcodqqok.luwebs.com/31004526/the-best-side-of-vanity-ethereum-address