The additional features and applications of competing crypto-currencies such as include increased security, better money management systems and improved payment times. Since the element of bitcoin's value that is non-speculative is based on future real-world applications, if other crypto-currencies are more likely to succeed in achieving widespread real-world use, more of bitcoin's value can be said to be speculative.
For worldwide money, you need an industrial-strength, dedicated network. Bitcoin is that. Folks running Ethereum nodes for a worldwide currency application would also incur processing costs for the CryptoKitty application, and every other. Those costs mean it'll never be able to compete with dedicated platforms on dedicated networks. Ethereum is a prototyping and coin-launch platform, not a production platform.