Because men who claim to be women don't want to be excluded on the basis they're male, and instead of acknowledging women's rights & needs that inform those rights, want everyone acquiesce to the lie that males can become female therefore female only provisions entirely unaffected by their presence.
The conflict is in the delusion that female rights cannot be erased by males who claim to be female because 'they're not the problem, men are'.
There is no squaring the circle of males who say they're women, making female only spaces/services/provision mixed sex by their presence/inclusion. I don't think anyone wants to leave someone in need without support or help, but the sacrifice of women's need to female only provision to accommodate the needs of males wanting to be thought of as women, isn't a price women should be paying.
There's nothing wrong with creating the all inclusive spaces that would be ideal for both TW & women who are happy to use/frequent mixed sex spaces. That would be the sensible & logical route to take. But that's not enough - it's the co-opting of every spaces/service & removal of female only for women who want/need it that's the aim for trans activists.