I plan on receiving social security. I can't imagine why anyone would not plan for it.
I don't intend to need social security, but those future monthly payments are definitely included in my retirement planning spreadsheets. So is my pension, my Roth IRA rollovers, my TSP withdrawals, my future rental income, and my expenses. Everything is only estimated, of course, but it baffles me why someone would go to all the of the trouble of trying to plan out their financial future, and then deliberately do it wrong by leaving stuff out.
Like if you're trying to balance your checkbook this month, why would you deliberately leave out your tax refund? You might not know exactly what it will be, but you know it's going to impact your finances and you should probably make an estimate and try to plan around that.
So I worked through the calculations. I downloaded my history of SS taxes, I made the required assumptions and worked through the equations, and I determined my projected future monthly income at a fixed future date. Then I added that amount to my spreadsheet as future income, in my case starting in 2042. Ditto for my partner's social security, our pensions, our mortgages, our rental incomes, our inflated expenses, and each of our investment accounts. I've plotted my projected checking account balance at the end of every month between now and age 100. And if you haven't done this exercise, or something very similar, then I might suggest you're not quite ready to retire yet.
The 4% rule is a handy ballpark estimate, but we're talking turkey here. Do the math for real before you make any irreversible decisions, and build in whatever safety margin you think think need on top of your best guess calculations. Social security is part of that process, and it should absolutely be included.