Bi-directional payments can be done using Full Node and no need for LN hubs. The principles of LN can be applied to Bitcoin and therefore tx fees would go to miners and Full Noders. Thus securing the network in the future when POW reward/subsidy goes down.
A full node with open LN channels is what is called an LN hub, no ?
The problem is that such a thing needs you, as a full node owner, to lock up quite a lot of BTC into the channels with your neighbours, and not settle before you've done quite a lot of transactions through those channels, because you only get small fees for the LN transactions, and you will need to pay a big fee to settle the channels on chain.
So the higher the amounts of BTC that you can lock up in channels, and the higher the amounts of BTC that your partner nodes you link to can lock up in channels, the longer your channels will "live" before being exhausted in one direction or another, and the more profits you can make on the LN as an active BTC locking hub.
This means that the benefits essentially will go to those whale hubs that can lock up a lot of BTC into channels with one another, and with "their customers", which are the small fish, that can never hope to set up LN links that will last long enough to reimburse the fee of the settling.
So you essentially get the whale banks that are linked with big LN links to one another (replacing the central bank settlements in the fiat system), and customers, linked to them with all their holdings, not able to settle because of the high fees, and completely at the mercy of their bank/hub to which they are connected.
Note that on the LN, you are at the mercy of your link partner, because any of you can decide to settle (and hence have both of you pay a big on chain fee). So a LN hub has all interest to be only connected to "secure" partners that will not easily settle: other big hubs, or dependent customers. Most probably, with other big hubs, the fees are 50/50, and with the customers, 100% of the settling fee is for their account. The central hubs can then also decide to whom you can pay, can report it, can help collect taxes on it, can stop transactions if they don't like them...
If the LN is processing about 1000 times more transactions than the chain can handle, you figure that settling on chain is a "one in a thousand" action, that is not easily done by a small fish, especially if the miners have already pre-sold the block chain room to the big hubs and "savage" transactions have almost no room.
