If Apple does this, it will most likely be through a third-party provider. That is already their business model. Apple Credit is through Goldman-Sachs, and Apple Cash is through Green Dot.

They will likely want to insulate themselves from possible regulation having to do with becoming a "financial institution" by letting someone else do that part. The regulatory scrutiny a big company like Google, Apple, et al. come under is the biggest hindrance to them adopting BTC/Lightning in my humble opinion, and is the thing that needs to be lobbied and changed.

Until there is legislation in place that clearly defines the responsibilities of "wallets," "custodial," and "non-custodial," along with the tax implications of holding and trading in BTC, I seriously doubt any of these companies would actually wade in directly, as that red tape is firmly the expertise of financial corps.