What's the technical problem with Lightning? What is making the exchanges hesitant from integrating it to complement their service? Plus are there business development people behind Lightning Labs to handle onboarding the exchanges and other institutions?
Aside from what @jackg said and classical problem such as "why bother upgrade if it's not broken" or "the code is poorly written/have no proper documentation", there are few specific concern (both technical and non-technical) such as :
1. What happen when a channel is closed, but the used on-chain transaction fee is low and there are many pending transaction on mempool?
2. Most LN implementation (e.g. LND and c-lightning) are still on beta, which isn't acceptable for most exchange and writing their own LN implementation isn't an option for smaller exchange.
3. Educating customer who don't know their LN wallet doesn't accept incoming transaction
I actually made a comment about this in the gambling section, because I asked why they accepted lightning for deposits but not withdrawals. They replied working on it but difficult.
I actually see their point. If you go to deposit and it fails you still have your BTC and you can try to figure out what is wrong.
If they try to send you BTC and it fails, they have to figure out what is wrong on their end, or your channel, etc. I have played at some casinos that have lightning deposit and withdraw and when the withdraw failed it was a real pain to figure out the issue. Turned out to be one of my channels but 1st thing I did was ask them what they were doing wrong.....
-Dave
For trivial amounts of money it's not a big deal if someone has to wait for everyone to figure out what is wrong, for larger amounts it is a big deal.
But.....
For trivial amounts it's not worth the time and effort to setup lightning for them. For larger amounts I could see it being a support nightmare.
How many posts here do you think we would see with people complaining that they were not getting 0.025
BTC funds from exchange XYZ while the exchange is trying to explain the largest channel they have open is .0245
BTC-Dave