google says "because css pixel ratio" but I can't figure out what that is, or why it exists.
Why am I adding metadata that tells the browser to render the screen at <2/3rd the screen's resolution? Images (as far as I can tell) don't get resized, so why is everything else? and why this so common?? wts is going on??
You need to understand why you are adding certain codes into your file. You said you have <meta name="viewport" content="initial-scale=1"> in your code. What initial-scale means is, upon page load, the page will be viewed at 100% zoom level. It's not about filling 1 CSS pixel to 1 hardware pixel. It's about filling 1 CSS pixel to 1 device-independent pixel.
As defined in Google's developer reference:
Device-independent pixel (dip): A scaling of device pixels to match a uniform reference pixel at a normal viewing distance, which should be approximately the same size on all devices. An iPhone 5 is 320 dips wide.
Hardware pixel: A physical pixel on the display. For example, an iPhone 5 has a screen with 640 horizontal hardware pixels.
Are the hardware pixels on your phone different from those on your PC monitor? Yes, they are different in terms of size (pixel density). Assuming your 21" monitor and 5" phone screens both have 1920px x 1080px screens, so obviously the pixel density is much higher on the phone's screen (and much smaller pixels) and it would not be wise to show up the webpage using the ratio of 1 CSS pixel to 1 hardware pixel since everything will be too small on the phone screen.
So what if you don't want responsive website design, but to fit the whole page into the small screen like what you see on a PC monitor? All you need to do is to remove the <meta name="viewport" content="width=device-width, initial-scale=1"> line and browsers will automatically fit the page onto the screen by default, by zooming out (i.e. initial scale will not be 1). Developers only add this line of code if the website needs to be responsive, and has the relevant CSS media queries for that.