It seems like many of the people here are very narrow-minded. There is more than one way to skin a cat.
The majority of people here seem to think only about the end-game. "Well I pay off my mortgage I gotta work until 50 instead of 45.," for instance.
What about the time in-between though? I'm only 29, even if I save and budget to the max at my current salary and spending level I'm looking at 45 at the earliest. Do I really want to spend 16 years at minimum budgeting to the maximum?
If I can pay off my mortgage and it allows me to have enough free cash-flow to maximize all my retirement accounts, and still have all the money I want to go and play as I see fit while still in my working years, is that not worth more than pinching pennies for 16 years and retiring a few years earlier?
Everyone's priorities are different. Some people may view your way a saving as inefficient because you can't get to all that money until you reach FIRE age. I would argue it's more efficient to spend a few more years working to live the way I see fit, for a longer portion of my time living, and during my youngest and most able-bodied years.
Of course, if you accept that on average shares have a higher return than your mortgage interest rate, this doesn't matter.
Say, simply if your mortgage repayment is $1000 a month, and you have an extra $1000 a month to do with, as you wish.
So, you have two choices.. lets say at just $1000 it takes 30 years to pay off the house, and if the full $2000 is used it takes 13.
So, either, you can pay $2000 off the house for 13 years, and then have $2000 to do whatever with, or
you can put $1000 into shares, and $1000 into the house. After 13 years, if the shares have grown at their historical rate, you will then have enough in the shares, to stop making house and share payments, and thus also have $2000 to do whatever with. If the shares have outperformed, not only will you be able to make the next 17 years of house repayments with them, but if the shares have outperformed, you will not use all of the shares, and you will have an amount of them left - dependent on how big the out performance was.
This is just maths speaking - if you're dubious setup a spreadsheet and run some scenarios.
But in the end, this just goes back to my previous points, paying off the house vs shares really just comes down to what someone's risk tolerance is.