"Roland Perry" wrote

No, the reason is because Cross =rail's funding was hard to get, and
doesn't pay to get all the way to Reading, and in particular won't pay
for the remodelling of Reading that would get lumped in if Crossrail
were to go that far. What many people expect is for Crossrail and
Reading to get their works done from their separate budgets, and then
benefit from a "fill-in" from new money.

Paddington to Maidenhead is 24 miles, and on to Reading a further 12 - so
even without remodelling Reading it will cost quite a bit to wire on to
Reading. However, Reading to London passengers would be unlikely to use
Crossrail if it ran from Reading, as it will be much quicker to take a
non-stop HST to Paddington, and change to LUL or Crossrail there. So
terminating Croassrail at Maidenhead makes good business sense and
operational nonsense.

Peter