You don't understand, its not the web-server, it is the client's browser that is the issue. Until SNI came out, the handshake was made and validity of the key

You don't understand, its not the web-server, it is the client's browser that is the issue. Until SNI came out, the handshake was made and validity of the key determined even before the "Host: xyz.com" header was sent in. Without the host header your webserver can't determine which key among the multiple sites it hosts should be used for authentication. The only way so far to support non-modern browsers and to host multiple SSL sites on the same server is to assign one IP per site; the server can use these IP's to lookup the respective keys.