I find this annoying. What you spend isn't the major problem. The major problem is that you can't count on money to remain of the same value with each passing year.
Since that silly fool got elected in 2008, the price of most of what I buy, doubled. Virtually everything I purchase in my day to day life costs twice what it did in 2008.
What good does it do you if you calculate you will need X dollars per year for 20 years when the real life costs of everything become 2X?
I don't see many people discussing the problem of rampant inflation of money, and no matter how you calculate your retirement, when the cost of things double or triple, most people will not be able to weather it without serious reductions in their standard of living.
Any good projection should take into account the value of inflation. Your point is valid, but to ignore it while doing a forecast is folly.
If you assume three things in retirement: 1) That your mortgage will be gone, 2) that your grocery bill will be significantly less and 3) that your property taxes will be significantly less,
then it is reasonable to assume that your costs of living will be a lot less. Yes, you will factor in Healthcare costs unless you are very lucky/healthy. But those are the major costs that I mention above and I can tell you, when I retire and we leave New Jersey, those three items will be reduced by almost 100% compared to what they are now.
That’s a big deal.