Because you don't use a blockchain unless you really need it.
Despite some of the hype, blockchains are "incredibly inefficient," "It's worth paying the cost when you need the decentralization, but it's not when you don't."
Blockchain is a revolutionary new way of sharing information and is clearly a valuable and transformative technology—but cryptocurrencies are just a fad, the latest bubble from tulips to tech stocks. So, why care about cryptocurrencies at all? In truth, the two are inseparable
What is a blockchain?
Blockchain is a term widely used to represent an entire new suite of technologies. There is substantial confusion around its definition because the technology is early-stage, and can be implemented in many ways depending on the objective.