[exim] Newbie question on queues

Hello All,

Just starting out on Exim and a bit confused as to the purpose of
queues. If my email campaign software is firing off outbound emails to
the Exim MTA and Exim subsequently connects to remote SMTP servers to
deliver the mail, then after smtp_accept_queue_per_connection = 10
starts dropping them in the queue for delivery later, what's the purpose
of this?

It seems to me delivery issues present when Exim is making direct remote
SMTP connections to the mail servers will also be present when the queue
runner starts later and delivers all the messages in the queue anyway.

I know this seems like a simplistic question but trying to get a grip on
all the Exim parameters.

Thanks.