Of course, he's in his 30's, and has a wife and two kids, a hefty mortgage, car payments, and the whole bit. The idea of actually owning anything at this stage in his life is alien to him. And it was to me, when I was 30.
His argument is that the interest on the mortgage is only about 5% or so, these days, and you can make more than that in the marketplace. But it is a flawed argument.
(Note that when you pay 5% in interest, it is not on the amount of your payment, but on the overall balance, so the beginning of any loan is almost all interest).
Of course, back when he was 30, those tax deductions were awfully sweet - and there is no way that age-30-Fred would have started a Roth IRA back then. So the point is moot. Age-62-Fred is stuck with the decisions that age-30-Fred made. And they hate each other - that's typical.
You have only so many years left to live, so it makes sense to take out the maximum amount, in your bracket, and pay the lower tax rate, than to take out lump sums later on, and pay higher tax rates.
Not having a $2000 a month mortgage payment is like getting a $40,000 a year raise in pay!