How long do you think it takes simply to open a LN channel for every BTC user with 300000 daily onchain transactions limit?
For 30 millions bitcoin users it will be like 100 days if only transactions recorded in blockchain is  LN settlements. We probably have much more users. And blocks already full, so there is no room for additional LN settlements.
Only coinbase alone reported more than 13 millions users in November 2017.
LN channels should also be closed, restarted, refilled, etc.
There is no way LN  ever will be adopted  by all bitcoin users.