That's the thing. You don't understand it. Three assumptions are made, and all of which are implicitly understood by those who understand the model of LN. They are:
1) A single payment channel is enough for you to transact with everyone (routing).
2) Everyone that you want to transact with is on LN.
3) Everyone has already opened a payment channel.
Assuming 10 million users (random metric), calculate how much block space it would require for each user to open a payment channel. Please post your results.

Anyhow, it isn't exactly recommended for high value transactions at this time
I don't quite see your point
If a single payment channel is enough for me to transact with everyone, why would each user be required to open a payment channel, and why would it require block space at that? As I understand the technology behind LN, its main advantage consists specifically in lowering the load on the blockchain since transactions made via payment channels are off-chain transactions, right? So why is there a need for the block space at all if these transactions are never to show up on the blockchain?