Samourai ignored lightning completely too, while it would have been the best post mix tool they could have implemented.

Coinjoins have people spending millions of sats on privacy, and it would have been incentive alignment to see the sats you spend on privacy also open up useful channels afterwards.

If you believe coinjoins are too expensive to exist with mass adoption, then you also believe lightning will not exist, as there were much higher fees to coinjoin, and yet approximately 4000 more bitcoin was in unspent whirlpool than was on the Lightning network.