4tph was introduced some years ago (c2004?) by extending the Weybridge/Staines shuttle to Waterloo via Hounslow. This may not have been unconnected with the fact that the Loop is one of the few lines operated by SWR (SWT as was) to have any real competition, as it runs close to the Piccadilly Line. Stagecoach, of course, had form for this srt of thing in its bus operations. Service enhancements elsewhere in London were never going to happen on Stagecoach's watch as they had, and SWR still have, an almost complete monopoly of rail services in SW London, with only two stations in the borough of Richmond, and none at all in Kingston, served by anyone else.
A little publicised "strategic consultation" last year proposed running the rounders only between Waterloo - Brentford- Twickenham. Protests from the LB Richmond that the stations at Whitton, St Margarets, North Sheen and Mortlake would therefore lose half their 4tph services (except, in the case of Whitton, by going the long way round or changing at Twickenham) were of no avail. On the contrary, the off peak rounder service has now disappeared altogether, leaving another seven stations (Barnes Bridge to Hounslow inclusive) with 2tph.
And yet SWR proudly proclaim that off peak travel is back to pre-Covid levels.