I am starting to think that part of the reason we have a reproduction crisis is because both genders find the bottom 80% of the opposite gender physically unappealing.
Obviously actual relationships are valuable, but dating apps tend to cater to hook up culture, and for people with friends sex is usually more urgently missing in their life than some degree of companionship. A lot of incels are actually more tilted by the feeling of being worthless/unattractive/unvalidated than the lack of companionship.