This! I'd argue that the only reason loyalty might not always matter is because I am frequently not given a real choice because a given route likely has a very limited number of airlines offering flights and those might be dramatically different in number of stops, price and times. Air travel is one area where I frequently wonder how many benefits of it being a free market on paper we are actually getting. There is limited choice and direct competition seems limited
One of my semi-frequent routes is between MCO (current home) and ABY - a small airport in Southwest GA where my parents live.
There are only two commercial flights a day, both on Delta and both to ATL. A round trip ticket is $540 for two 1 hour segments (MCO - ATL - ABY).
A round trip ticket from MCO (Orlando) to LAX (Los Angeles) is about the same price
Of course I know the trick for former - book through a partner AirFrance for 17K miles