This can be a well-reasoned strategy for some. Arbitrage between the (assumed fixed) mortgage rate and the return on investment elsewhere can lead to an advant

This can be a well-reasoned strategy for some. Arbitrage between the (assumed fixed) mortgage rate and the return on investment elsewhere can lead to an advantage if you simply leverage your equity in the house rather than locking it away. This has been a workable strategy for a number of decades, although it isn't historically so.