Nobody said that ATSC/DVB Tuners were supported, uvideo(4) handles UVC devices only, video(4) is a device independent "V4L" compatibility layer.
No drivers have no written to support such devices, porting them from Linux is a bad idea, GPL is only compatible in one direction.. can't have GPL code in a BSD project. (
Though honestly, GPL proponents fail to understand the BSD licence and violate it often.).
video(4) was only recently developed, only uvideo(4) uses it... but, with that in tree, a motivated developer might write a driver for a ATSC/DVB tuner they own, it probably won't be a LKM though.
It's still early, but I can tell you.. not many will be interested in the concept of recompiling a Linux driver for usage on *BSD.