Why do people think that having a crush means you're automatically in love with that person?

I have always wanted to know why people think this way. I personally don’t think crushes equal love. I mean it can grow into love, but it’s not love right off the bat. It’s impossible to fall in love at first site or whatever it’s called. You can fall into a strong lust, but love at first site is not real, imo. How do you feel about love at first site and crushes automatically equaling love? I think it’s stupid.