I believe your concern is right but blockchain is also a new and useful technology in some aspects. The main feature about blockchain technology is about the cryptography, how the technology helps secure the transactions, data, record keeping or security. The technology is not mature yet while it may not be applicable to all the applications or service sectors too. The decentralised network is an alternative way in transactions or other actions other than the centralised.
We should not limit block chain technology to crypto currencies only. Blockchain is a vast technology and can be applied to many fields of life. The best thing is that it is decentralized and we can use power of distribution rather than limited centralization.
Its already being use in so many ways not only in crypto currency. If you are you will find so many companies using blockchain as source of monthly allowance provider and some are using to save their data. Banks are also now adopting blockchain and they admire the reliable way to save money with the help of blockchain as its well developed technology.