img pointer to image not automatically adding width and height

Recommended reading about CSS Containment.

https://www.smashingmagazine.com/2019/12/browsers-containment-css-contain-property/

Nor should it.  How long is a piece of string?  It varies.  It's the same with images.

Image height & width is determined by:

• Native image size,
• User's viewport width,
• Parent container in which the image resides.

To reduce bandwidth consumption by mobile devices, optimize images in Photoshop and export to 1x, 2x, 3x sizes.  Use the <picture> tag with SRCSET attributes to serve appropriate sized images to various devices.

Example:

<picture>
  <source media="(min-width:650px)" srcset="largest_image.jpg">
  <source media="(min-width:465px)" srcset="medium_image.jpg">
  <img src="mobile_image.jpg" alt="default" style="width:auto;">
</picture> 

Or if you're not that ambitious yet,  use the following style rule in your CSS code.

img {max-width:100%}

Browsers will rescale the image to fit whichever device the user has but not more than the image's native file size.  The only downside to this is that mobile devices consume more bandwidth than they should.

Hope that helps.

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