However, there are many teams who either don't have the knowledge/expertise, or the available time, to do the testing themselves. This is where "buying it off the shelf" can come in handy.
Then, there are teams that are completely clueless when it comes to application security, and even the most basic scan by any of these pen testing vendors will find very obvious security defects, which is absolutely valuable for them to learn about. This is the minimum bar that we should hold software application developers to, and there are many who don't even meet this without the assistance of reports from pen testing vendors. Scary, but true.
So, YMMV.
I've had to wave off a few managers who got unsolicited emails from vendors saying they found or know of vulnerabilities in their site(s) and for just $MANY they can fix them.