Why does the power cord on my new Samsung Samart TV detach?

If you want it to stay put instead of pulling itself out as you rotate it...
Get some of that BLU TACK clay/rubber stuff. It is for sticking up posters...
Anyway, knead a small ball. like a 1/2 inch ball of it stretching it folding it until it is nice and sticky.
The roll it out into a worm like tube 2" long.
Wrap the tube of goo around the base of the plug with the plug IN the socket, making a wrap touching the TV and the plug equally. Press it down firmly on all sides.

The goo will come away if you pull the plug. but will be sticking to stuff too. Use the ball of goo you can pull away to 'pick up' the little bits stuck all over the plug and the TV socket

You can re-use the ball of blu tack over and over.
The stuff come in different brand names too.

I use it for a lot of my AC plugs and have reused it for YEARS.

If this is too gooey..
Use a wire clip and screw the cord to the TV at some screw already on the TV.
The fastener I would get is a tube open to allow a wire in, with a set of tabs with screw holes to clamp the held wire in
There are also sticky types of those, but they often fail to grip well.

One reason is in case you mount the TV on a wall and run the PC behind it.  You are supposed to use an aftermarket cord that's rated for that.  Not everyone does however.

It's so you can change the power cord to a better one.  It makes the green look more green, the yellows will really "pop", and Donald Trump will look a more natural shade of orange.

Because SAMSUNG SERVICE SUCKS, so it makes it easier for the technician to carry out the panel only. 😬

I am the proud owner of a new Audioquest NRG-1 2-meter power cord for my LG Smart HDTV. Hey, gotta better than the stock cord. $50 new on eBay. Solid core rocks!  It’s a no brainer. 🧠

From Audioquest’s web page:

No matter how perfect an AC power source, distortion is added within any AC cable, especially within a stranded cable. Even the most sophisticated filters and power supplies cannot eliminate this cable-induced distortion.

FEATURES

SOLID LONG-GRAIN COPPER (LGC) CONDUCTORS
Long-Grain Copper (LGC) has fewer impurities and fewer internal grain junctions, reducing distortion and digital timing errors.

STAR-QUAD HYPERLITZ GEOMETRY

COLD-WELDED CONNECTORS
Cold-welding bonds the plug to the wire using high pressure, not high heat. This ensures that the character of the wire is not changed at the point of termination.