Why does anyone book with agencies?

My wife had a trip booked which was $80 more for paid first then the fare paid for coach. I wanted to reissue it, but the agency in question (I was not responsible for the original booking or payment) decided to close for the day, and the window the cheap first fare expires today.

My second attempt calling Delta got a reservations agent to get a supervisor who agreed to halve the $150 change fee.

In the end, $209.92 still seemed worth it for a confirmed upgrade on a flight which otherwise wasn't letting a non-Medallion assign a seat at all, so I sprang for it.

Total cost:

$365.70 base fare/tax
$24.00 agency booking fee
+ change:
$50.00 Delta fee to reissue agency issued tickets
$75.00 "half off" change fee
$84.92 difference in fare
---
$599.62 total cost
vs:
$450.62 total cost if booked on, gee, Delta.com, Orbitz, or virtually anything else.

Golly!