Unfortunately there are a fair amount of people, within those communities, who feel as though attention placed upon trans issues not only distracts from gay/bi issues, but that it is a very different issue and as such should be separated from the movement entirely.
I should state that I do not believe in their views, I have volunteered for and attended Pride festivals without judgement, however I felt it was important to give an explanation to their ethos (as far as I understand it, anyway).
That’s where being pansexual has the upper hand: I don’t even have a clue.