Browsing through old stuff at thrift stores can reveal how much tastes have changed over the past several decades. When the change has gone against your own preferences, thrift stores offer an oasis of things that you'd buy if only retailers still sold them.
In the "wall decor" section, you're bound to find portraits, whether original works by a local painter or photographer, or mass-produced prints. Two that I recently picked up were a print of Senora Sabasa Garcia by Goya, and a wooden plaque with The Carpenter by folk religious artist Frances Hook.
The plaque with The Carpenter is from the early-mid '80s, and the Goya print looks to be made in the '70s (judging from the dark, faux-grain wooden frame). Back then, portraits were in high enough demand among the public that mass-produced copies sold well. Now they're stuffing the shelves at thrift stores. Each of the pick-ups was under five bucks, a sign of how little demand there is today.
Interest in people wanes in cocooning times, so it's no surprise to see autistic contemporary shoppers ignoring portraits when choosing what to put on their walls. If you browse the best-selling items at art.com or allposters.com, you'll see very few portraits. It doesn't matter whether you search all categories of posters, art, photography, etc.
When human subjects are shown at all, it's usually as part of an activity, where their animation is determined by the action they're engaging in, rather than a more probing look into their personality and inner nature. Then there are the scenes where they look like lifeless dolls, an emo approach to glorify or glamorize passivity and fatalism. See these two top-sellers from allposters.com:
These are in the same vein as other popular dorm-room high art, such as The Kiss by Klimt and any Pre-Raphaelite work.
Also popular are landscapes and cityscapes (suitably devoid of people), abstract or impressionistic buildings and flowers, personality-free animals (owls, ostriches), and the odd piece of technology (vintage cameras).
For a look into how dorm room walls used to be adorned, see this image-packed post at Business Insider for pictures from the 1890s through today, all at the same university. Portraits were a staple on dorm room walls in the '60s, '70s, and '80s. Even when animals rather than people are the animate subject, they are shown in an attempt at a character study, as though the animal had its own personality and nature.
Pictures from the previous cocooning phase of the Midcentury do not show anything at all on dorm room walls, perhaps a sign of the "don't show off" norm of the time. But I already covered the decline in portraits on the covers of the Saturday Evening Post (see here). There was a peak during the 1910s and '20s, then a decline through the '50s, when they were replaced by the types of scenes that have become popular again today (activity scenes, landscapes, technology, etc.).
This investigation shows the comfort around vs. distrust of strangers in outgoing vs. cocooning times. But I think you see the same mindset applying to people you know and are even related to by blood. Back in the '80s, every living room had a full array of photographic portraits on the walls (some of them must have been hanging there since the '60s and '70s, since they were taken back then).
Now it's considered cheesy to see close-up pictures of people in someone's living room. It's not a reaction against over-sharing, since these are your own private domestic spaces, and in cocooning times you are very rarely going to be visited by guests, let alone for a long time or on a frequent basis. It's you yourself who are weirded out by close-up pictures of your own flesh and blood.
Again, you may be comfortable displaying action / activity scenes -- here I am, touring Rome; here I am, skydiving for the first time; here I am, having drinks on my birthday; and here I am, building a house with Habitat for Humanity. Actual portraits, whether of you or someone you know, trigger the intimacy alarm.
It's such a strange mindset compared to 30 years ago, when the living room had portraits of many different individuals, and multiple portraits of a given individual to capture the full richness of their personality.
Related: a three-part look at how Seventeen magazine covers have changed between the '80s and the 2010s (here, here, and here). The covers from 1985 are all portraits, while the girl on the current covers is only meant to display clothing and to wear a kabuki face that shows how epically you'll be crushin' it if you buy These 8 Must-Have Smartphone Accessories.