Surely it needs to at some stage, otherwise, great though Lightning is, it will never be reliable enough to really take off? So that must link to fees, and while it's great to move sats free of charge that simply cannot be sustainable...

I believe big and well managed nodes are already profitable. At one point I earned in routing fees the cost of VPS which hosted that LN node too (that node is gone now).

In my opinion the reason lightning nodes are not really profitable at the moment has most to do with the software we use to run them.

Manual node management will never reach profitability (the time you spend managing your node has cost).

I see it primarily as a software problem. The capex on a small node is low, this should only scale if you need to hold substantial liquidity on the node. The opex is too high only because you have to use your own time to figure out and manage liquidity/channels.

There’s nothing about running a profitable lightning node that can’t be automated (in my opinion).