Watchtowers are not trusted parties and you do not have to be always online to be secure. There is a configurable period where you can broadcast a revocation transaction. Watchtowers can do it for you but it's designed so they cannot frame you. The penalty for broadcasting an out of date transaction is loss of all funds in the channel.
To summarize.
1. Attacks are extremely unlikely in the first place.
2. Watchtowers can prevent them if they do happen.
3. Watchtowers are trustless. They in no way resemble banks.
4. Without a watchtower you are not required to be always online to be secure.
You think the LN doesn't exist? What? There are dozens of LN visual explores out there. Who told you this lie?
The whole point of using LN is to use Bitcoin as a settlement layer. You make one initial transaction to open a channel and that's it. In the future users will onboard directly into LN channels anyway. On chain scaling is still important. Ethereum 2.0 will likely do over 10,000 tx/sec. Don't know about Bitcoin.
To summarize.
1. Attacks are extremely unlikely in the first place.
2. Watchtowers can prevent them if they do happen.
3. Watchtowers are trustless. They in no way resemble banks.
4. Without a watchtower you are not required to be always online to be secure.