I think most people confuse love with lust.
They fall in lust, not love.
By the time the lust has been used up, they are usually living together, maybe she's pregnant, things happen which are difficult to extricate themselves from, so they just carry on regardless. They call this situation "love".
That's not to say something akin to love doesn't exist, I think it does. It's that strange attraction you might feel for somebody, not exactly sexual, at least not overtly. More the subtle joy of proximity. The rush of excitement you feel when they are in your company. The needless touches, the glances, the ease of being together. Where you suddenly realise they are beautiful without being aware of when this happened.
Lust is primal, it's instant, there are some people who you look at and just want to fuck.
Love I think is not rational, lust can get you into trouble, love can make you lose your mind!