I'd say there are a few different groups, each with different motivations. What you mentioned is definitely a part of it, keeping the gravy train of various charities going. Those people can go fuck themselves.

Then there are the "I'm alright, Jacks". The ones who really know it's bullshit, and will likely change their tune the second switching sides will get them more social credit. These are often married or elder gay men and lesbians. The ones that know chanting TWAW/TMAM won't ever affect them, because they'll never be expected to prove they believe it ("Sleep with a trans man? Oh, not me. I'm married"). They can also go fuck themselves

Then there are the ones who have for lack of a better word been hoodwinked. They've been told it's exactly the same as the fight for gay rights, and they haven't done enough reflection to realise it not only isn't, but is in fact an actively homophobic movement. The problem is when the T was first added, there was some legitimacy to it, since at the time most of the people we'd think of as old school transsexuals were gay men with internalised homophobia. And that's the image that comes to these people's minds when people say "It's exactly the same. They fought for your rights, dontcha know?"

And then there are the ones who are just plain scared to speak out. As things gradually move, we'll probably see more of these people speaking up. The problem is they'll also provide a convenient shield for the second group, who'll claim that they were also simply too scared.