I don't think people under rate it. The issue is that BSD is so much server focused in users and development and it lags behind Linux Desktop (which is still a small percentage). There is just a high amount of programs that are not available in BSD.
I use to have me personal server as BSD and used FreeNAS quite a bit. Due to lack of certain "cool" applications I wanted to run on my machine I just switched to BSD.
From my perspective, the BSDs are focused on what they should be: making a good version of Unix. I feel that the Linux developers are spending too much effort on the "desktop", which is why we have now have GNU/SystemD.
I use to have me personal server as BSD and used FreeNAS quite a bit. Due to lack of certain "cool" applications I wanted to run on my machine I just switched to BSD.