Not that we should go around calling people 'neckbeards', it's rude, but there's a reason the term exists.
And of course being more attractive makes life easier. Did I say even once that it did not? That's blatantly obvious. But do you really actively think about if strangers that you happen pass on the street or in a store find you hot? This is what she described.
Everyone cares what some other people think of them. Friends, family, collogues, and people they're attracted to, etc. Some people care more, some people care less. But, I think, most people don't really care too much what complete strangers think to the point where they actively think about it while passing them by. Or do they?
Beyond that, I think it's extraordinarily hard to not care what strangers think of you. Not a particular stranger, but just strangers as a whole. Depending on where you live (e.g.catcalling is more common in particular cultures or more metro areas), you can have people commenting on your appearance every day. After years of that, of course you start noticing the comments being more or less nice, or more or less frequent, and I imagine it's easy to obsess over it. It should be pointed out though that it's clear the author doesn't enjoy obsessing over how men think of her - I imagine these are more intrusive thoughts.
I enjoyed a feminist lit book with similar themes of a character who embraced being 'unf*ckable' called "Dietland". The 2nd half of the book goes off the rails but the first half was thought-provoking to me, for anyone who might be interested.
I will try to read it!
You've never wanted to be attractive to whatever gender you're attracted to? I find it surprising that this can be "totally foreign" to any human that's not asexual.
Being the most attractive version of yourself that you can be isn't just about sex, either. It really does open doors socially and economically. Right or wrong, people enjoy the company of people who put thought and effort into their appearance. And if for no other reason, your partner certainly appreciates it!