Why do I like to watch them? Can't explain that fully, but I also find watching the flows in ntopng to be fascinating. Maybe I'm just easily entertained. As far as why I would run pfsense over OpenWrt or similar, it's mainly what I know and I can drive the pfsense bus well enough. Back in the day I experimented around with OpenWrt, and it may have improved over the years, but I found it kludgy.

ETA: Also to do IDS/IPS you'll have to install Suricata, Snort or SoftEther anyways so......