Consent forms have issues because they can never be specific enough, but may still be useful for some people.
It is worth having a discussion, especially in horror, about what players may be comfortable or uncomfortable with. I know some people that think consent forms and related tools can help with that discussion. I personally do not use them as a GM, because they are simply never specific enough.
For instance, people that may be perfectly comfortable with a game that includes murder and violence in graphic detail may become incredibly uncomfortable with the same thing involving a child in any form. I have dealt with more than one player like that.
Also, things change. People normally comfortable with horror and murder in games may not be comfortable with it for a time after a close family member dies. I've seen this happen too.
Similarly, you might find someone that thinks a mention of sexual assault as part of backstory is perfectly acceptable (and its a common starting point for a revenge rampage in horror), but would find details about it uncomfortable. For that matter, you may have disagreements over what constitutes "detailed".
Personally, I find a general discussion supported by X-Card's far more useful. They provide a simple way for a player to communicate with minimal effort that the current topic is unpleasant.
Also, this question is highly related and may be useful.
As a side note, while this topic most clearly comes up in horror it is not limited to that. I once played a strongly lawful good character in AD&D until an NPC magically reversed my character's alignment and the. The DM described it as my character being inclined to do the opposite of his normal actions in all moral matters. The game was lighthearted and combat focused until then, but the DM quickly became uncomfortable, had a discussion, and invented a reason to remove the change on the spot.