I may be missing something—I wasn't sure what they were so I looked them up and I found the Wikipedia entry, which makes some mention of medieval lore of them being similar to incubi, but nothing about them being able to change sex at will. Alps don't exist in D&D either.
This has been the case since 2e. However in 2e their "True form" was always Female. In 3.5 they could be born either and just switch between, but one or the other is their "true form"
"Oh, hey friend! I just made garlic bread! It's warm enough that you can see the garlic butter oozing across the golden crust of the bread, and steam comes out when you tear a piece off. If you murder all your friends, I'll let you have some~"
And for the warforged: "sudo murder all your friends"
They're not actually sexy women with wings and little horns; that's just the form they usually use when someone summons them deliberately because it's the form most summoners want to see. They're malevolent, shape-shifting extra-dimensional entities, they're adept at emotional manipulation, they want to drain away a mortal's soul through physical contact, and they prefer having that contact given willingly. (Maybe the soul is more useful to them like that, or maybe it just tastes better.)
They don't need to seduce you. Maybe being a mercenary has severed your bonds to your family and your community? Maybe you've seen things that you wish you hadn't? Mommy understands. Mommy will make you all better. Give Mommy a hug...
If anything I think that makes it all the more valuable that they go to all that effort anyway. Who doesn't wanna be wined, dined, and have-their-soul-drained-leaving-nothing-else-behind every once in a while?
Every character I play is secretly asexual, and I don't think anyone has realized yet.
The closest I came to come out of the closet was when my Undead Warlock married his Unseen Servant. It was his best friend, they looked up to one another, respected each other, and shared an exclusively platonic relationship.
He prepped the entire ceremony in secret as part of multiple sessions:
He asked his mentor to put a 6th level Major Image inside his spell storing trinket, which he used to create the perfect setting for the altar.
He took a dragon scale from the corpse of a dragon the party had slain, and spent money to have an engagement ring crafted out of it.
He had an outfit made out of very expensive material for the Unseen Servant.
He put the Unseen Servant spell inside a custom wondrous item that gave him infinite casts of a 1st-level spell.
He asked the party's cleric to cast Ceremony.
He then waited for the final battle, and the night before, he gathered everyone without telling them why, took out the ring, cast Unseen Servant and proposed to it. There were a lot of happy noises that evening, especially from the party's cleric :)
The character I'm playing now is a lawful good city watch who is "married to his job", and the Paladin has joked multiple times about taking him to a brothel. Bruh, take the hint.
How does a succubus sex up someone without genitals to sex with? 🤔 And I don't mean how the power of charm works, I mean mechanically. What are they doing?
Can it not be like sirens singing about your deepest desires to lure you in the water. So asexuals get sung to about snuggling in a blanket with a hot cuppa of Coco.
Maybe the charm of the succubus could be the same for sexual tensions. What they find most desirable to find in others.
The warforged could see the best artificer who is able to understand all the intricacies of your function.
A monk sees a teacher who is able to gently guide their way to mastery.