> Eh, the Lightning Network has been a thing long enough that the appropriate question is no longer "when will it be ready?"

The same could be said for bitcoin. The reality is bitcoin still suffers from a scaling flaw, one that appears to be unfixable. The workaround is to layer any entirely new protocol on Bitcoin, Lightning. It has been 4 years in deployment. It is couldn't be said to be successfully deployed as Lightning's creators have noticed bugs that make it unsuitable for prime time. https://medium.com/@antoine.riard/why-we-may-fail-lightning-...

I'm no expert, but they don't appear to be bugs that run as deep as bitcoin's scaling flaw, however they do require changed to both bitcoin and Lightning to fix. And implementing the fix is bogged down by the need to keep the patient alive and functional during the operation. The serious mistakes created by a "moving fast and break things" doesn't work for this style of project.

And for "why" bitcoin / Lightning isn't working splendidly after all this time, I think it's fair to say creating a functional digital currency that is secure and scales infinitely turned out to be far harder than anybody imagined, and I'd say far harder than anybody could have possibly predicted.

Lightning is still relatively new, one of the answers to the "why" is that none of the large wallets such as Coinbase / Cash App support it yet.

Once it gets a few user-friendly wallet and merchant apps, I'd expect to see adoption. Especially since it's much safer for merchants as they do not need to wait for confirmations, and transactions fees are fractions of a penny so merchants actually benefit compared to creditcard interchange fees.

Why do none of the large wallets support it yet?

It's been well over five years since the Lightning white paper. By this point in Bitcoin's own timeline, the MtGox scandal was in rear view mirror; in another year, the Lightning network will be as old as Bitcoin was when Lightning was proposed.

If Lightning is going to provide the mainstream digital currency Bitcoin promised but failed to deliver, why is it taking so much longer for Lightning to be adopted than Bitcoin?

Lightning is pretty complicated, it isn't quite as clean and simple a protocol as Bitcoin. Bitcoin uses a broadcast protocol whereas lightning needs more complex routing and nodes need to lock-up funds via an on-chain bitcoin txn to make a connection.

The internet itself at the backbone/isp level is a decent analog as ISP peering can be complex and often involve cost. It took awhile to get BGP right and determine the right cost metric for selecting a route.

There don't seem to be any blocking issues though and many of the large wallets have announced that they will be supporting it eventually.