In my profession, we rely on generalizations. For the most part, they work (did you catch that? Yeah, generalizing is easy to do). One such generalization is that fir floors are soft wood, as opposed to oak or cherry (or a myriad of other woods) which are "hardwoods". Hardwoods are typically more desirable as a floor covering, because they weather abuse better. You can walk around in stilettos or your dog can run on the floor with his un-trimmed nails, and it won't dent or chip the floor. For the most part, this generalization is true. The trees harvested and milled today are barely 30 years old. 30 years isn't very old in the tree world. However, the trees milled to make the wood floors in most of Portland's old houses, were, on average, around 200-300 years old (depending on the year the house was built.) I spoke with a client just the other day, who had done some major remodeling on his house. He'd pulled down an exterior wall, and instead of 2x4's (the lumber typically used to frame a house today) he found 2X6's. This wood looked so interesting and the grain was so tight, he decided to salvage it and send it to a local mill to make wood floors for his remodel. The miller who processed the wood said it was 1000 year old Douglas Fir. He said after 1910, there were no trees left of that age. (His house was built in 1895.) This fir-which would typically be considered soft-is harder than most "hard-woods" on the market today.
So although fir is most often a soft wood, there are always exceptions to the rule.