ELI5, why do people put profits into a 1031 vs a tax write off

[Mitchell Rusten]

Simply put, why do real estate investors need to put their profits on something like a flip into a 1031 exchange rather than simply putting the profits into a new property and writing off the acquisition like a normal business would? When McDonald’s makes a profit on a hamburger, they don’t have to enter the framework of something like a 1031 exchange to avoid paying the taxes on the profit and using it to buy more hamburgers, they just write off the acquisition of more hamburgers and don’t pay taxes on it until they eventually decide to step out and stop their continuous acquisition of more profitable hamburgers. Other than when a property can’t be found before the end of the tax year, is there a reason I’m not aware of that says you can’t make $40k on a flip and use buy 2 houses for $20k + hard money and avoid taxes rather than having to abide by the rules of a 1031 exchange?