Why does google chrome need so many ports open?

They are the local port numbers of the sockets connected to the servers that host the websites you're browsing right now.

In TCP/UDP socket communication, there is always a port associated with a socket. For both the receiving and the sending side.

HTTP most commonly uses port 80. 443 is most commonly used by HTTPS.

The local port numbers have no real relevance or meaning. It's nothing to worry about.