Daniel Bowen wrote:

That's called (at least in some countries) "live to tape", and is still
common in news and current affairs.


I love this aspect of Doctor Who - I think it contributes to the
aesthetics. Live TV drama is pretty much nonexistent these days, but I
find the 'almost live' quality in classic Who very exciting and
spontaneous. I get kind of a thrill when things go wrong - I've been
watching 'The Aztecs,' and it cracks me up no end when Hartnell and
William Russell keep stepping on each other's lines in Episode Two. I
understand why they wouldn't do 'live to tape' in this day and age, but
I miss it!

Michelle