Because they both pull at your heartstrings. Lust gives you rose-colored glasses that disappear usually after a nut. Love perseveres
after the nut. Hell, love technically doesn't need the nut. Lust is your body and hormones doing battle with your head to fukk somebody. Sometimes you never
know which you are feeling until you either :Fornicate with the object of your attention, or so much time passes, you either get pissed off or indifferent.