Judas Priest 1978 Stained Class tour...
Judas Priest 1979 (Around the time NWOBHM broke) Killing Machine Tour
See the difference?
And there's the change of musical direction as well, out went the slower proggier songs and in came the much shorter faster commercial songs with razor sharp guitars, which is something that pretty much defined the difference between the early 70s metal and the NWOBHM as a whole.
That's why they're included.