Real estate broker here.
Everyone likes good hardwood floors, but most people who prefer hardwood are still cool with carpets in bedrooms. I feel that way as well. I have hardwoods throughout, but area rugs in the bedrooms. Rug or carpet is simply more comfortable in bedrooms. I’ve had people who disliked the carpeting in bedrooms of houses because of its color, style, or being in poor condition, but I’ve never seen anyone object to good-quality carpet in bedrooms of a house with hardwood floors - even if the hardwood under the carpet is in good condition.
People generally like to have a contrast of wood and carpet/rugs in the house. What people tend to dislike is wall to wall carpeting. The kind of carpeting that covers every inch of every surface of the house (except for the kitchen and bathrooms…but sometimes even them too…UGH!) Nobody ever likes that.
Homes built before the 1950s tend to have hardwood floors. Depending on the preferences of the owner, they may have carpet over the hardwood. If the homes are single-owner or have been inhabited by only a handful of owners over the decades, the hardwood is often in excellent condition underneath the carpets.
Homes built after the 1950s often do not have any hardwood. Frequently I’ll have clients who eagerly pull up the register (air vent) in a house, hoping to peek under the carpet and find hardwood, only to be disappointed when there is nothing there but subfloor. Often 60s and 70s ranch or split-level homes have a combination of hardwood and carpet, but in the areas with carpet (usually the bedrooms, sometimes a den or rec room) there will be no hardwood under there. In these instances people typically replace the old, dated carpet with newer carpet or with hardwood or laminate.
Contemporary homes typically have medium to wide-plank hardwoods, arranged in a staggered pattern like brick masonry. Earlier homes from the 40s or 50s often have “slat” flooring: long, narrow planks, all arranged vertically and parallel to each other, and nailed down in the same spot. This type of hardwood doesn’t seem to be installed any longer, since I’ve never seen it in a newer-construction home.
Gaining popularity in recent years is a type of flooring that is made to look like faded wood, but is actually a ceramic-like tyle. It can look cool in houses with gray/white modernist looks, but doesn’t fit well with “earth tone” palettes at all.
I also occasionally see hardwood floors that have been painted over, usually in a dark brown or black color. I don’t like how that looks, but a lot of people don’t seem to mind it at all. It’s typically found in quick-and-dirty flipper houses, usually early-1900s or late-1800s houses that were renovated on a tight budget.