Google Flights isn’t a third party portal! It takes you directly to the airline web site to book. It attempts to estimate the fare price but that’s becoming increasingly difficult with variably priced seats and other “gotcha” expenses that get figured in deep into the booking flow.

For domestic flights, perhaps. It routinely refers me to third party OTAs for the cheapest prices on flights to less common international destinations.

And in that case, this was never regulated by the government. The airlines shouldn’t be responsible for how their products are presented on a random aggregator.