When we renovated our house in 2005, the utility and shower room we had put in downstairs was perhaps the best thing we ever did. Before we just had the washer and dryer in the kitchen as normal, and got along just fine no real problems etc.
However, since we had a utility room we've often wondered how we did without before. Although ours is a very small and narrow room - it is such a useful space. First off, it's used as the dog's bedroom - handy to lock dogs away etc. Secondly, it means the noise of the washer and dryer (albeit very little having Mieles) can be shut off from the rest of the house. Thirdly, it means we can bulk buy detergents etc as the big boxes will fit in the utility room with no hassle and can be left out where it's convenient rather than away in a cupboard. Fourthly, it also means we can leave the ironing board and the clothes horse up all the time - convenient, but also out the way. Of course, also being next to the back door (the old kitchen didn't have a back door, so you had to go all across to the back door at the other side of the house to hang out washing), it means you can hang laundry on the line which starts baically right next to where the washer stands without having to use baskets.
Not just that - but laundry itself can be organised without having to use the landing as we did before. We can sort out and leave baskets of loads out in the utility room, rather than having them all along the landing as we used to before. It also means the ironing pile, and clean washing can be stored in there in people piles. Very useful when you have a family like ours, that benefit probably isn't there if it's the typical couple household.
They're probably not a necessity, no - but neither is it a luxury. In my opinion they're intelligent uses of space, and it also means the kitchen looks a lot nicer and sleeker. Now we have fully integrated appliances in the kitchen, it is so much easier to keep clean - without having to pull out the washer, dryer, dishwasher and fridge to clean behind.
The house I'm moving into for uni in September has the washer in the kitchen, but the dryer is in a cupboard under the stairs which potentially can be used as a utility room as it has a worktop. Great to be able to store piles of laundry and the ironing pile!
Jon