Paying off the mortgage is a high risk/low reward proposition and is a viable strategy only in a limited number of situations.
Those situations don't appear to be very uncommon for people on this board, though. I think they're mostly related to tax optimization.
One of those situations appears to be qualifying for ACA subsidies, by reducing your taxable income generated by 401k rollovers required to pay your mortgage each year. That's easily worth $10k per year to an average family, especially one that carries a very large mortgage that otherwise precludes them from getting subsidies. The expected premium from carrying your mortgage is almost always worth less than that and is far more variable than government issued insurance subsidies, which are basically guaranteed if you do your paperwork right.
Another appears to be having high school age children who will be disqualified from financial aid considerations for the same reason, because even if you have no real income your taxable income on paper is too high after making the annuals rollovers required to pay the ongoing mortgage costs. If you eliminate $30k/year in mortgage payments, suddenly you can get by on a super low annual spending rate.
I would love to be corrected on either of these points, because I'm seriously considering paying off my primary mortgage this year by selling a rental property. In one sense, I would just be moving RE equity from one property to another, but it also means giving up a bunch of RE leverage. Maybe that's a good thing, if the local housing market turns south.
My risk tolerance appears to be dropping considerably in retirement. Now that I've "won" the FIRE game, I no longer need to gamble on 10% market returns. My plan is totally safe with 2% market returns, I just need to avoid -40% market returns. I'm happy to give up the possibility of ever crossing the $10M threshold in exchange for guaranteeing that I never go broke. Suddenly, products like annuities make a lot more sense to me than they did two years ago.
Note that this is the exact opposite of Telecaster's post above. He said paying off your mortgage is a high risk and low reward gamble, and I'm considering paying off my mortgage in order to have LESS risk in my overall portfolio. I would love to find options for where to park the proceeds from the sale of a rental property, somewhere that I can access them for living expenses (and hypothetical ongoing mortgage payments) without generating taxable income for the next ten years or otherwise disqualifying myself from the ACA or simplified FAFSA. Because right now, home equity in my primary residence appears to be the best place to put that money.
Help me, friends. I seek your financial guidance and wisdom.