[2020] Why does Striker not work with Shotguns ?

I've passed the issue of Striker indifference to shotgun shells along to the team.

As saagri mentions though, striking a balance between the automatic shotguns vs. something like a double-barrel can be tricky territory.

100% for sure. Main potential drawback is just having only specific shotguns be viable with Striker, where the difference between best and worst option is a huge range (somewhat reminiscent of TD1).