To be fair most COTS solutions made for enterprises are absolute crap. It doesn't take much to improve upon them.
Enterprise tools are well-known to have absolutely horrible user experiences, extremely complicated configuration and architecture, and even worse documentation. I don't blame any manager/PM for thinking, "we can do better" with an internal team.
It's saying your engineers are so much more precious and able than the barbarians outside the gate, that they should write their own test harness/DOM selection library/insert commodity software genre here.