But is has been infinitely long that certain environments blocked the
ports that GMail requires for POP/SMTP and quite long that they
blocked the ports needed for GMail IMAP (simply because it is more
recent).
For users in environments that block those ports then the Webmail
extension requiring *only* http (port 80) access did and continues to
do a great service to those users wishing to access their GMail in
those restricted environments.
There should be a FAQ for the Thunderbird Webmail Extensiosn - we
would not need to keep answering this question.