One thing to note, usually a yard space if on a different level to whatever the room is attached to, so that in the case of a leakage from the washing machine, only your yard will be affected.

Also, usually yards have a drainage hole, which make it convenient to move and position your washing machine as long as your water out hose can reach it. If in the kitchen, your washing machine has to be stuck in 1 location only. Also usually yard has plug points that are higher than normal to allow easy access for washing machines.

Most people with units without balcony would also greatly appreciate yard space as it is usually uncovered (add grills for safety), so that you can dry your clothes.

For smaller units as well, some use the extra space in the yard to keep their utility items/soaps/detergents/tools/ladder. If not it has to be kept somewhere inside in your bedroom or somewhere unsightly.