In rooms/areas we "entertain" most, we - as normal human beings - want to show how well off we are. The highest quality in wooden flooring are selected more often for these "reception" areas than lower quality floors. These areas also get the highest amount of traffic and the wooden floor has to be more sturdy and durable.
In bedrooms however it is more down to what is most practical, both budget wise and health wise, to install. Many manufacturers have 'low' budget ranges - still good quality! - for these areas. A simple 3-strip Oak Rustic comes to mind.
On average we spend 7 - 9 hours a day sleeping in our beds, a rather large uninterrupted part of the day to be in one single room. In this respect, installing wooden flooring in bedroom is a wise and healthy decision.