Because that's grammatically correct by today's standards. "Become" would typically be in the context of "have become" instead of "am become" these days.
This is intended to be a community where Chicago Blackhawks fans can come together to discuss anything related to our Hawks. I am trying to gauge interest, so please subscribe and I will have it up and running soon. Go Hawks!
This is intended to be a community for Chicago Cubs fans to come together and discuss everything related to our Northsiders. I am currently trying to gauge interest, so please subscribe and I will have it up and running soon. Go, Cubs, Go!
Because that's grammatically correct by today's standards. "Become" would typically be in the context of "have become" instead of "am become" these days.