Why is Bitcoin Cash worth less than BTC?

The value of cryptocurrencies is completely up to supply and demand. At this point in time, there is simply more demand for BTC as many people find it suitable for their purposes.

For the time being, cryptocurrencies in general are mainly used as speculative assets rather than alternative currencies. While Bitcoin Cash continues the peer-to-peer cash design of Satoshi Nakamoto and BTC has abandoned that use case, BTC still enjoys name recognition and perception as the “original”. Therefore, the very much improved capabilities and accessibility of Bitcoin Cash isn’t necessarily reflected in market prices.

Of course, users can benefit from many of Bitcoin Cash's properties and use cases no matter what the market price happens to be at any given moment.