The lightning network is hard to make simple user interface for. A lot of wallets are experimenting with different models. Muun chose to pay for lightning invoices with onchain transactions at the time of payment. The problem is that in high fee environments, like we have been in recently, you pay ridiculously high fees for lightning payments. That’s my high level understanding. One thing to note with phoenix, you should try to make your first transaction pretty large because that’s what will create your lightning channel and so you will have to pay on-chain fees for it