I've written a couple of long screeds here about how commuters are really something of a problem for the railway. What is boils down to is this:
1. Commuters with season tickets get a whopping discount compared to walk-up fares
2. They travel at peak times, morning and evening
To give every commuter a seat would require
vast amounts of rolling stock that would make perhaps only one or two revenue journeys a day (so over a week perhaps just 10 productive trips), then spend the rest of the time either running around empty using electricity/fuel or sitting in a siding, all the while costing money for maintenance, capital costs etc.
There's nothing new here, it's always been the same. Bluntly, it's not affordable, economic or even feasible to give all commuters a seat. The late Gerry Fiennes wrote about this dilemma during his railway career (which started out on the
LNER» in the 1930s and continued until he reached very senior positions in
BR▸ management in the 1960s before being de-frocked by Barbara Castle for writing a somewhat controversial memoir,
I tried to run a railway).
Edited to add...
Re the Gold Card, looks like the whole of the North Downs line qualifies, so from what I infer about your journey if you had an annual season it would be a Gold Card.
FGW▸ also runs occasional promotions for season ticket holders such as
this one which from a quick read looks like it allows travel anywhere on the FGW network in first class for GBP20.00 return at weekends, although I haven't read the small print.