Just as bisexuality has been unfairly associated with promiscuity, there is a bad stereotype of pansexual people out there, which suggests that just because they have the ability to be attracted to people of any gender, they are somehow immediately attracted to anyone they meet.
To get away from this unfortunate and unrealistic promiscuous stereotype, based on little more than anecdotes here and there, some pan people prefer to identify as panromantic.
This means they can have a romantic attraction toward someone of any gender. This phrase is also useful to mark out a difference between those who can find themselves sexually attracted to people of any gender - pansexual - but not necessarily romantically attracted to people of any gender - and therefore not panromantic.