“While there are exceptions like Yaakov Avinu even when it was allowed the norm was one wife.”
Not just Yaakov aveinu
ALL the cases I can think of involved special circumstances either a melech, or one wife couldn’t have children
Avraham, Yaakov (who was tricked), Elkanah, Dovid, Shlomo
of course we find Eisav and Lamech though not exactly role models
Any others?