Well if you don't know, ChiefPlanner, who does....?
The Colne trains used to mostly terminate at Preston, with some going to Blackpool North. The Blackpool South trains ran as (mostly) a shuttle service to/from Kirkham & Wesham. In 1987 the South trains got a bit of a boost with hourly, clock-face trains to Preston, at which time they were tagged on to the Colne trains where they've remained ever since. Operationally it's probably a bit of a 'mare for all concerned, and they seem to run late more often than on time. Despite that NetworkRail keep looking at splitting the service at Preston and always decide against it on the grounds that having to change trains at Preston would be a net "disbenefit" to passengers.
There have been the odd Colne - Man Vic through trains over the years (historiaclly they always went via Accrington and Bury 'til it closed). None of them lasted long becasue the journey via Blackburn took too long. It's quicker by bus.
Sorry to diasagree with PR1Berske (judging by another thread you'll be well used to it by now though!
), but your memory is playing tricks on you. Apart from a single M - F daily service from Clitheroe to Morecambe which ran for a while, Clitheroe trains have always run through to Manchester Victoria - even historically before the line originally closed in the 50s (not sure how far back you're talking about.)
(Apart from the summer Sundays-only DalesRail from Carlisle to Preston/Blackpool - just remembered them!)