Dairy calves aren’t suitable for beef production, generally.
That's also not that true any more. A lot of what people believe to be true of the dairy industry is now at least a decade out of date.
Dairy Cows are often artificially inseminated with 'sexed semen' vastly increasing the rate of heifer (female) calves being born and reducing the amount of bull calves.
Dairy Bull calves that are born do now have a healthy market in the beef industry, they are fattened and sold (not as veal) and the meat is increasingly sought after by supermarkets etc as its very lean.
Many dairy farmers are also crossing their dairy cows with beef breed bulls like limousin or Hereford and the resulting calves, male or female are sold into the beef industry.
Most dairy producers (e.g. Arla) make being in a Red Tractor scheme a condition of being one of their members, and often also stipulate that male calves can't be culled at birth. Not that anyone would these days anyway because male calves currently have a value.
A lot of what people think they know about dairy at the moment comes from the very dark days after BSE etc where British beef sales were on the floor.
I'll happily admit that some practices in the British dairy industry aren't ideal, but it's also not anywhere near as bad as some people like to make out and by and large dairy cows lead very pampered lives. They are the supermodels of the bovine world.