Carpet used to be the most popular floor covering around, but its always had its problems. Dust and dirt get trapped in carpet easily, making it difficult to clean, and likely to start looking bad and aggravating peoples allergies over time. It is also difficult to have carpet in nice colours, as light colours are much more prone to being stained by dropped food or drink, necessitating the use of expensive cleaning products that may not even work.
Hardwood flooring solves all these problems. It can be light-coloured while remaining easy to clean, as there is no way for stains or dirt to get attached to it. Wood floors also tend to have interesting natural patterns, which are usually much better than the flowery or swirly-patterned carpets they replace. Also hardwood, as opposed to softwood, will not dent or scratch if heavy objects are dropped or placed on it.
Of course, this doesnt mean that hardwood flooring doesnt have problems of its own. To begin with, it is often expensive, as natural materials must be used instead of synthetic ones. It also tends to take longer to lay, as it must be laid in strips instead of being cut to size and laid all at once as carpet...