I noticed older homes built through 1930s generally have higher ceilings and taller baseboards and thicker mouldings around window and doors vs homes in the 1940s. Most of the homes here built in 1940s still had solid wood paneled doors, wood frame windows, but shorter baseboards and narrower mouldings, but still with some detail but only 8 foot ceilings. Houses built during the 1950s-70s started to have very skinny baseboards and trim with no detail, and hollow core, flat doors, and aluminum window frames. Newer houses are still basically this way, but the mouldings have more detail again and in some cases wider, and most doors although hollow, have panel details to them. Also a lot of newer houses here have higher ceilings such as 9-10 foot ceilings or vaulted ceilings, but most in the 1950s onward had 8 foot ceilings only. Some of the 1960s-70s homes only had 7 foot ceilings.

Why did houses after the 1940-50s get plain vs older ones?

The population (quantity of people to build houses for) grew by many times but the available resources to build houses with didn't, and in many cases available time to finish the building didn't either

So resource use and time requirements had to be minimized, and new materials that are more industrial processing friendly, or just cheaper, were tested to replace old materials

Some of that came for the better like Aluminum window frames

Some of that came for the worse like Aluminum wiring

Resources were cut also in engineering - most often by making a design once and then building entire quarters of 10's of identical buildings in cities. In the Soviet Union, they sometimes even flattened natural terrain over the entire area to be built, in order to be able to place the boxes by the ruler and not optimize the positioning for each building individually

And many times resources were cut in workmanship - Sometimes decided in the last moment on the site and resulting in nasty defects hiding in buildings, like missing rebar elements, that was let to slip through because deadlines

Energy efficiency also started to become a concern around this time.  High ceilings are nice, but don't provide much additional useful space.  However, that space still has to be heated or cooled.  Also keep in mind that those old homes from that time often lacked anything in the way of insulation, and what they do have was likely added later.

The block that our flat is in was built in 1979, and is of concrete construction, with very good insulation both sound and warmth. Plus the rooms (not that there are many of them) are of a decent proportion.

We count ourselves as being very lucky to have a property like this, and it's on an assured tenancy, so unless we really screw up then it's safe for as long as we want it.

I lived in a house in Fairbanks, Alaska built in 1941 that had only 7'-6" ceilings, small rooms, and tiny windows.  Had hardwood floors under carpet I ripped out for my roommate (the owner of the place).  We figure the walls are insulated with sawdust. 

I lived in a house in Sitka, Alaska as a child, built in 1955 and since demolished, that had only 6-6 ceilings, again tiny rooms. All 2x4 construction, even the roof joists!  It had last been redone in the 70s or 80s as evidenced by the wood paneling, popcorn or accoustical tile ceilings, and various dated types of carpet or linoleum.

I lived in a house in Tyee, Alaska, built in the 60s or 70s as a kit home but moved out there complete from Petersburg on a barge.  Its moving was a story I learned while living there, but it was almost an A-frame.  Panabode snap-together type setup.  So hideously dated with the baby blue bathroom fixtures and harvest gold kitchen counters (and aluminum wiring) that it was almost cool (Save for the ZInsco panel!)

My childhood home in Atascadero, California was built in 1988 and had high ceilings and large rooms.  Being in a warmer climate, though, I can see the logics of the 8-2 ceilings, etc. 

My current home is built at umpteen different times out of salvaged materials, so "dating" the architecture fads doesn't really apply.

When I first moved back to Aberdeen, the flat I shared was probably built in the first few years of the 20th century. I then moved to a block that was built in the 1960s, and the last move I had before getting my present flat was again built in the early 1900s. What happened to that flat is the reason I got this nice warm modern place to live.

During the Second World War, there was a Luftwaffe raid on the coal yards that were opposite to where the flat was, and it suffered from some minor damage. This over the years got worse and finally in 1993, fifty years later, the council condemned the property. They were legally obliged to offer me alternative accommodation, so I got out of the nightmare that is the private rental sector.