There are through buses via the Mersey road tunnel to Liverpool from Neston, Heswall and Upton which are more direct and a better frequency
Exactly, Upton is my local station on the Borderlands Line (Although I'm actually nearer to Birkenhead Central/Green Lane). Still, Upton is within walking distance and I do walk there quite regularly.
I use Upton for daytrips in to North Wales, but I would never use it to go in to Liverpool, even if I lived next door.
There's a 10-minute frequency bus service (437) going in to Birkenhead and Liverpool which stops near to the station. (Was every 7 to 8 minutes uintil a couple of months ago).
All local public transport users use that bus, instead of an hourly train service where you'd have to change after just one stop.
Also the railway line does not go straight (as the crow flies) to Liverpool, it's more of a circuitous loop around the north of Birkenhead. All things equal, the bus probably isn't any slower (although I'd have to look this up). In fact this bus service sometimes accepts rail tickets during times of disruption on the Borderlands Line.
I read on a local Wirral history site that there were originally plans for a shortcut railway line passing through Tranmere and Prenton, connecting Birkenhead Central directly to the Borderlands line near what is now the Woodchurch estate, but nothing ever came of it (apart from the fact that the layout of some streets in Tranmere betray the presence of the originally safe-guarded land).
Neston - Similar public transport situation except it's a half-hourly bus service into Liverpool.
Heswall bus station has several bus routes in to Birkenhead/Liverpool and the railway station (formerly "Heswall Hills") is nowhere near the centre of town, in fact it's on a "suburban-rural fringe".
Also, like myself, many people in more built-up areas of the Wirral are nearer to a Merseyrail station anyway.
I have noticed that the Welsh part of the Borderlands line is generally busier e.g. Gwersyllt seems to be quite well used.
As for Buckley, I travel there quite a lot at weekends and it's a station where always quite a few alight and a few board, despite the fact it's around a mile east of Buckley town centre.
So if the figures are showing the Merseyside end has lower figures, then I'd say that's about right.