"I think our school's gone crazy"? Nah, it's a rather natural thing, especially in Hentai.
Even her friend (probably) does it...And even she does it...It's a perfectly normal thing.
I would say the opposite. I read it as the lead girl was a side character in every other story where people lost their virginity and in the final chapter she loses hers. As the wrap up for the book she happens upon all the happy couples. The same thing happened in Yamatogawa's Aqua Bless.