Why do people assume that all bisexuals sleep with anyone that comes up to them?

Lack of knowledge, LGBT+ stigma and biphobia. I'm a pansexual and some people thought I could have sexual intercourse with "animals and plants"

I think it's because they assume that since bisexuals are attracted to both genders, that they'll take whoever comes up to them and wants to sleep with them.

When it comes to sexuality, people often misunderstand that the ability to be attracted to someone does not mean that you will. Since bisexuals *can* be attracted to two or more genders, people tend to think that they will. A solution to this is to turn it around on the person, i.e. "are you attracted to every member of [gender(s) that person can be attracted to}?"

Because people are stupid and think that just because we're attracted to multiple genders, we'll sleep with anyone

Well if people like that thinks so thats their opinion. Remember that you are the boss of yourself and you are in control of what you believe in.

Because people are uneducated and think that bisexuals are greedy when in fact they are not, what we need is these kinds of topics to come up in classes so that kids grow up knowing what's true.

Because people suck and they listen to sterotypes. I think people are getting better at avoiding them, but eh.

Because bisexuals like both genders. Which basically means people sees them as the "sexuality whore" in a way. But that people say this does NOT mean it is true. If you're scared people think this is true, just ignore them. They cannot decide who you are.

This is just me trying my best...because I am not sure but...maybe people think because we are open to being with both genders that makes us...promiscuous? I don't think that way...though I am bisexual.

Because they are labouring under the misapprehension that sexuality is a choice, and by showing attraction to both genders it is because bisexual people are greedy and/or desperate. Some bisexual people may have multiple sexual partners, and that's okay if that's what they want. But by definition, bisexuality is simply experiencing sexual attraction to people of either gender. They are just as likely to be in a committed monogamous relationship as any straight/gay person.