[lxgr]

I suspect that the commission that Google presumably gets for each referral played a much larger role than a desire to not be transparent. Google Flights is not just a search engine – they get paid by the airlines, as far as I know!

As far as Southwest being listed on OTAs is concerned: I'm pretty sure they always have been, or I wouldn't have bought a ticket with them a while ago. They're just apparently not on all of them.

[rockostrich]

AFAIK they aren't on any OTAs. I just checked Expedia and Booking for a route that I know they have inventory on (PHL to DEN).

[lxgr]

Not sure what Chase Travel uses, but I booked a Southwest ticket on that back a few months ago.