Governments don't want people to travel unless absolutely necessary.
That is because the science shows travelling / mixing / sociallising increases risk. An excellent paper in Science shows how much suppression is produced by each restriction
https://science.sciencemag.org/conte...cience.abd9338
While there is little evidence closing borders has much effect once the receiving country has significant occurrence, the general advice to not travel is based on science. Are we really suggesting airlines help clarify the mixed confusing messages from government and actively discourage people buying tickets?