Why can't I import a Bitcoin Core private key into an Electrum wallet that supports Lightning?

Question

Why can't I import a Bitcoin Core private key into an Electrum wallet that supports Lightning?

Running importprivkey in the Electrum console, I get:

Error: This type of wallet cannot import private keys. Try to create a new wallet with that key.

When I create a new Electrum wallet with the private keys, why is Lightning disabled for that wallet?

Answer 1

🎩-tip nc50lc on BitcoinTalk:

Electrum's lightning wallet requires a master private key where the private keys to be used in your lightning transactions' HTLC (Hashed Timelock Contract).

It can't rely on imported keys since it'll eventually run out of available unused keys after few transactions and reusing those isn't an option because it's unsafe to reuse used keys in old HTLC.