Two of my brothers work in a quarry,they don’t get flexi time,one was in on Sunday morning last,I’d sooner employ a pair on agreed times than one full time,my tanker driver works 4 days on 4 days off,it works well.If you've a family, once you factor in childcare and the cost of getting to and from a job - especially one that may not have any clear career progression - you can see the lack of appeal.
With the rural nature of farm jobs, I'd not touch one that didn't come with a house. And a house that was dry and well insulated at that.
A job at £15/he sounds great. But take off the tax; the diesel at £1.75/Lt; the car to get there and back; the extra childcare because they won't let you work flexi or from home part of the day; pension contribution; etc.