In my opinion they can be at first, but ultimately you shouldn't go by looks, looks change over time and can become very different. If you love someone for what's on the inside they will always be as beautiful as the day they met.
I don't really like any of those answers. There has to be some level of physical attractiveness, but for me if I'm interested in a girl her physical attractiveness is enhanced a hundred times over. She becomes literally the most beautiful woman in the world in my eyes. What I'm attracted to is HER, I'm not really attracted to physicality alone.
A few girls try to figure out what to do to look most attractive in my eyes, but generally they don't get that the best thing you could do to make me more attracted is to be shy, quiet, and thoughtful. If you have the personality I'm attracted to, I'll by default think you are beautiful.
I'm just going to assume your talking about relationships as casual sex is 80%(+) about looks.
Looks are not easy to explain, people always think "oh I'm not a supermodel so I can't get guys or girls" and they don't realize that its all about attraction.
If you met a guy YOU thought was attractive, then YOU would be interested in him even if your best friend lets say thought he was average or less. Same applies to guys, its all about how you are preceived by the other person.
Not all guys want the same type of girls, we all have a "type" that we like or are attracted to both physically and emotionally.
You need to have BOTH in the other persons eyes, he won't come and talk to you if he's not at least attracted to you but he won't stick around if your boring as hell(TO HIM).
I just put it in a you perspective, it works the other way around aswell obviously.
If a person doesn't have looks at all, I'll be honest, I probably wouldn't date her. I mean, how can I be attracted to her if she isn't physically attractive at all? However, if she has no personality (and only good looks), she also isn't going to get far with me. If a girl only has looks, I won't look at her beyond someone who looks good, and the only sort of relationships I would consider her for would be one night stands or friends with benefits (however the latter is technically impossible since I wouldn't be friends with someone with no personality).
So for me, a girl needs to have some good looks, and a good personality in order for me to actually consider her as someone I may want a serious relationship with.