Population of Chorley borough 2016 = 115,000
Population of Leyland South Ribble = 110,000
Population of Preston = 140,000
Population of Bolton metro borough = 300,000.
Why stop at Oxenholme (Kendal population 29,000) or Penrith (population 15,000 or Eden Valley 53,000)?? Or even Carlisle pop 101,000??!
Well, if we do as you suggest at Penrith, it gets left with absolutely nothing (only about half of all VT services call there IIRC); and Oxenholme just its hourly Windermere shuttle, which would have minimal traffic owing to the now completely non-existent connections at Oxenholme. Carlisle and Preston both have hoards of connections that Chorley, and many hundreds of other stations, simply do not have.
Anyway, population does not correlate to a justification or baseline of service level (cf. Poole, Rochdale and Lincoln to the likes of Barnham and Markinch). A lot of rail service provision is based on geography, circumstance and, in all honesty, sometimes a slice of good fortune - see the likes of Diss and Alnmouth.
(As an aside, how many of those thousands in Chorley borough do not find it more convenient to gravitate to the likes of Preston, Blackburn or Wigan for rail services regardless of what Chorley station offers? The borough stretches well beyond Chorley town and practically to the outskirts of other, much larger settlements.)
3tph isn't bad for a town of Chorley's actual town size (35,000): this is equal to what the three-times-larger town of Blackburn just 10 miles up the road received until a few years ago, and, as I've pointed out, in relative parity to other rather much larger settlements. I can appreciate the annoyance of gaining then losing such an attractive service as Chorley did, but to be genuinely honest, does it need an hourly service to Lancaster, Cumbria and Scotland, especially when the existing service levels to Preston make connections so easy? Unfortunately, the Scottish TPE services are one of those sets always likely to be beset by overcrowding, and adding more calls for what would primary serve just local journeys does not aid this (as I've said before, a huge problem I think for CrossCountry services).