I guess using video on location was not the easiest back in the 60s and 70s, needing an OB unit and several big cameras! Would have had to wait until the 80s for more portable cameras and presumably the ability to shoot single camera and edit more easily.
Lightweight cameras really were the key enabler for OB-style location video drama, and allied to that portable 1" VTRs also had a role in some instances.
The BBC shot quite a lot of video drama on lightweight Fernseh, Ikegami HL79s and Sony BVP330 cameras in the late 70s and 80s. There were occasional Doctor Who video location shoots when most location stuff was still 16mm film, and a significant amount of costume drama (Barchester, To Serve Them All My Days, Mansfield Park etc.) had location video (though in some cases film was also still used for some location stuff)
A lot of location drama was shot 2 or 3 camera and cut as-live with just the single mixer cut being recorded to 2" or 1" VT
(I think 1" really revolutionised this way of working) There were 'single camera units' (SCUs in BBC-speak) which used a single camera cabled back to a small OB truck with vision control, some basic sound equipment and a 1" VTR housed within, along with talkback. This style of working was particularly popular with Children's BBC productions. Camcorders were still not really available in any quality until the late 80s - and even Betacam SP wasn't really ever favoured for mainstream drama. (DigiBeta in the mid-90s brought the advent of location camcorder 'single camera' working to mainstream drama).