It is also measured in inches in Europe and it is weird. Electronics get sold globally and I guess nobody wants to discuss a "139.7 cm TV".
It's a magic number though and I cannot imagine the sizes. I just know that 55 is bigger than 49. It is the same with phones, where it is much less important as screen ratios "get improved" every year and the diagonal means basically not much.

When traveling in Japan, I do recall seeing TVs marked in inches. But in a world where globalization has made goods ever more accessible and affordable, this shouldn't be too surprising.

Another example of ostensibly American or British Imperial units, lots of plumbing around the world is sized in inches or fractions of inches. But even in the USA, there might not be any dimension which actually measures the same as the trade designation. For example, 1/2-inch Schedule 40 PVC pipe has an inner and outer diameter that is larger than 0.5 inch (12.7 mm). In the UK, I understand that they might round off these trade designations to centimeters, but I have no idea if that would then reflect their true outside diameter or if it's just a straight conversion of the trade destination.

Aviation also uses feet for altitude in most of the world, with even ardently metric countries like Russia changing in 2017-2020 from meters to feet. In all these cases, it's ultimately a matter of harmonization to reduce confusion and increase compatibility, either technically, procedurally, or economically.

I wouldn't call it "measured in inches" as much as they are "named" with a partly numerical name, which may or may not be an adequate correspondence with a different country's length scale.

It's similar with bicycles: many tires are named in inches. Two tires with the same number of "inches" may however not have the same diameter, so to translate size-names into measurements is fraught with pitfalls.

It's a bit like how in NZ you can order a "pint" of beer, and the bartender will fill up a random size glass around 400~700ml 😅: you can buy a 30" TV, and if you measure the diagonal, it's around 79-82cm 😅

Yeah, it is inches too in Southeast Asia. I guess simply converting current size screen to centimeter just makes the number awkward. For example 14 inches is 35.56 cm. If display to be measured in centimeters, I think the sizes will have to be different to make it marketable.

South America here. It's one of the few things where we use freedom units. And beer pints as some other pointed out.