And money! A lot of those big exchanges require huge upfront payments. It's crazy! Rome wasn't built in a day. I can see more coming onboard over time.
I noticed
https://info.binance.com/currencies/litecoin-cash <-- this listing, with a 4$ issue price. Hopefully that's what it comes online at

The Litecoin Cash team are working on new exchanges, LCC is only 22 days old, these things do take time...
To be honest, I think it is usually much easier for hard-forks to get listed because the holders of the original chain are able to claim it. If these exchanges don't list them, they risk their users moving to other resources to claim the free coins and staying there afterward.
There is also another incentive to support the fork as the exchanges are likely to hold a good amount of LTC themselves.