Indeed. Reading passengers should accept that some trains should be non-stop out of major London terminals for distances of 100 miles or more.
But it's not just Reading passengers. It'd be passengers from:
Reading, Heathrow Airport, Gatwick Airport, Slough, Maidenhead, Staines, Bracknell, Wokingham, Farnborough, Aldershot, Camberley/Blackwater, Guildford, Dorking, Redhill, Woking, Weybridge, Petersfield, Haslemere, Basingstoke, Newbury and a long list of other stations. Putting the airport traffic on one side, that's still a huge catchment area.
I would guess that GWR makes sufficient money from long distance tickets routed via Reading that any thoughts of running a significant proportion of peak time services fast through Reading would be quickly discarded.
The WCML example of splitting between Virgin WC and London Midland works because there is no major railhub on that line 30 miles from London.