Finding myself thinking back to Uxbridge (Vine Street)- West Drayton & Yiewsley 'back in the day'. Clearly for those responsible back then the rail business didn't cut it. There had been lots of 'plans' to connect at Uxbridge with either the Met (or Piccadilly) Line (or both) and/or the former GWR line down from Denham to High Street (or both) none of which bore fruit. Why? Such 'no-brainers'- ha ha! Who, honestly, would have used them? Why? I worked for Hillingdon Council in the 1980s; we built several hundred much-needed homes for folk on the former railway land- all near shops, schools, etc. That's over 40 years now in which folk have enjoyed living there, brought up families etc etc.
Watford is similar- good centre, jobs, good rail services, M25 and M1 access ... why not build on the surplus land?