Mind you I think the Readings are still Richmond-Clapham-Waterloo only, which is only one stop, which would only add presumably about 2 minutes. I guess congestion is the problem, though looking at some of those old BR-era timetables there still seemed to be a lot of peak services - BR seemed to be very clever at squeezing in a lot of peak services, more than today perhaps, without impacting journey times too much.
The Weybridge-Richmond then fast is I think long gone, I don't even remember that from the 80s.