Why do we think of reinvesting for IRR?

[Vlad Denisov]

Let's say we acquired property on a year 0 for 100k. Let's say we had a cashflow of 10k every year, for years 1 to 5 and on the year 5 we also sold the property for 130k. The question is why when we calculate the IRR, we do it as if all those cashflows were reinvested into the property? Because in reality when we get 10k in the end of year 1, we are free to do with it whatever we want and oftentimes we won't reinvest it in the property, right? So does it only make sense if we reinvest or I miss something?