Adoption will grow as the infrastructure continues to be built out. It's still early days for Bitcoin - no one sends AT commands to their modem to get online any more.
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.
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.
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?
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.
Lightning still has some rough edges (async payments) and unsolved issues (spam resistance) but it’s a lot closer to being a convincing private scalable p2p payment network than many realise.
[1]: https://breez.technology/ [2]: https://phoenix.acinq.co/