1. Unpredictable fees make usage for small amounts almost require a long-lived channel to be worthwhile.
2. UX around Lightning channels are painful. You can't receive BTC in a channel unless you put BTC in as collateral. You can't spend more than the channel allows. Routing is unpredictable and fickle causing transactions to fail just as often (if not worse) as complete successfully. (Perfect for one-off transactions /s) All Lightning wallets (with the exception of one or two) are custodial and if they aren't, they cost a lot of energy to run on your phone because they're constantly chatting with the network.
3. The whole point of cryptocurrency is diversify the control across the network. The design of Lightning motivates large hub and spoke connections between users which consolidate control to a few individuals.
4. The complexity for any business to integration Lightning into their purchase flow is expensive due to the many states your channel can exist in and need to considered as part of your integration. Not to mention the added costs of monitoring the BTC network to protect your channels. Or you find a merchant provider you have to trust with your processing...at which point, you're just using credit cards by another name.
5. And due to the complexity of Lightning's design, there are systemic bugs which expose users to more risk than if they just used a gift card or credit card in the first place. (One case in particular, a channel which is mostly settled on side B (versus side A) such that A's value on their side of the channel is less than the dust limit of the BTC network (which is often given the highly fluctuating fees) will allow B to force the close of the channel causing A to lose their value in the channel (because A will need to spend more than their side of the channel is worth and will be a worse outcome than if channel A just ate the loss from the channel being maliciously closed)).