Because the travesties there are, of course, continuing under their administration even though they highlighted them as a monstrous act by the Trump admin. That is why they are adverse to doing such a photo op - it would not be in the context of "resistance", but as "reluctant facilitator" (per their PR strategies), and they would rather not talk about it at all. It's also an opportunity for activists to protest and for journalists to ask more questions about their sociopathic policies.

It's a 100% downside situation for them, just damage control stuff.