OKC sold nearly 5000 head on Monday. If they sold them one at a time they'd still be there.
The bigger sales group like calves together. If you bring two 5 wt calves in they may be grouped with similar type and weight calves.
The singles usually have a problem, limping, too poor, horned, odd colored, and etc.
Sometimes they're are just mismanaged calves that need a little tlc and can be bought cheap
People that have a reputation of raising good calves and cut, wean and vaccinate are announced who owns them and what's been done to the calves.
Watch the Woodward sale on Friday and you'll see the ring man/owner giving the auctioneer a note telling about certain groups of calves.
IMO it pays to do it and if I'm buying I'd spend a little more for calves that I know have been weaned and vaccinated and likely to have less trouble with.
Edit
Stockers and feeders like groups of similar genetics , type, weight and etc so they're performance will be the same calf to calf