When you are lambing on a farm scale, the amount of work to look after orphaned lambs is significant. And you can find yourself all too frequently deciding on whether to spend time saving this lamb, or getting out and checking the ewes again - where a lamb or even a ewe could be being lost because you are not there to help.
It's different when you have only a handful, of course it seems easier to manage it all then. On the moorland farm we lambed the 80-odd mules first, and with two of us, it hardly seemed to impinge on ordinary life. Then the 400+ Swaleys kicked in and it was flat out madness for 17 days.
To sell them on, a conscientious farmer will make sure all lambs have had adequate colostrum in the first few hours, have fed well for at least 24 hours and seem well-established. That's the very bit of work takes all the time and effort!
So whilst I can't just leave 'em to fade away but have to try to save 'em, I can completely understand others making different decisions. And it doesn't mean they are heartless, just that they don't have the manpower to produce 'spare' lambs to sell on, and aren't willing to sell them on, badly or not prepared, to unsuspecting punters.