Yeah I can understand why the manufacturers have moved that way, especially as anything under 55" seems a bit pointless 4k wise but you'd think they would still be targeting the smaller bedroom size in some form.
The problem here is there's very little money in 'bedroom'-sized TV as a market. What happens in many cases is that the lounge TV gets relegated to the bedroom, so the bigger budget gets spent on the lounge set. That, or the thinking is "
it's only the bedroom" and so it commands far less spend on a new TV.
Having this mindset wouldn't be so much of an issue if today's lounge sets were a minimum of say a grand and all the TV manufacturers were rolling in dosh, but that's not the case. They've all driven out costs to the point where only a few big players can afford to be in the market. This is your classic price war; only the biggest survive.
The casualties are not only the smaller TV manufacturers but also consumers because choice gets stifled. You've seen this most obviously in screen size, but it's also evident in the range of TV brands. Under the skin, lots of once-household-name brands are really the same TV with a few minor tweaks. The big players in this market are Vestel (Turkey), UMC (Slovakia), TCL and HiSense (China). Broadly speaking, if your telly isn't a Samsung, LG, Panasonic, Sony or Philips then there's a good chance it came from either a Chinese or European contract manufacturer.
This kind of contract manufacturing isn't unique to the TV market and it's not something new either. Apple doesn't make its own products. China's Foxconn has been making iPhones and iPads for years. Many other big brands rely on them for manufacturing services too. Some Sony TVs are made in Slovakia by Foxconn. The entry-level Panasonic sets are made by Vestel in Turkey.
To summarise so far then, the TV market is going to hell in a handcart, and much of the momentum has been provided by the TV manufacturers themselves in trying to beat their competition and grab an ever bigger slice of the market.
Next we come to the role of the supermarkets in all this.
It used to be that TESCO et al competed on volume and price in just groceries, but they figured out that shoppers are pretty much a captive market because of how frequently they visit the stores. Why not then sell them consumer electronics, clothes, banking, insurance, holidays, gas, electric, internet, health care products, tyres and even dabble in second-hand cars?
Since the supermarkets have little experience in no proper infrastructure to support their consumer brown goods sales (TVs, STBs, DVD players etc), then the only weapons they have are the constant footfall of visitors and volume pricing. The result is that all the supermarkets gravitated towards the cheapest of any range they sell. As a consequence then, they seeded price expectations in customers minds based on selling them crap.
When they started out, if you looked at TESCO shelves, their most expensive 50" telly might have been say £400 for a recognised brand. There'd then be a second tier brand for £50 less, and a 'value' product at another £50 lower step. Contrast that with a proper TV retailer who would have the same £400 50" TV as their entry level model, but then stock two or three products with substantially better specs at say £500, £700 and £1000. Someone who spent maybe an hour a week in a grocery store and walking by their "top" TV at £400 would suddenly be faced with a massive change in reality. That's a bitter pill to swallow and no wonder so often the call is rip-off Britain. However, it ignores the fact that the products aren't comparable.
It didn't take too long for the supermarkets to realise they needn't stock ranges. Just offer something really cheap. It'll still sell no matter how poor the quality. This has a lot to do with why there's so little choice outside of what could be termed mainstream product ranges.