It (usually) does not, at least not for websites. Reading the screen would require a lot of computing power and be prone to mistakes, especially with unusual fonts and noisy backgrounds.

Instead, screen readers read a website‘s HTML source code which also gives the developer the chance to annotate how certain elements should be read. Accessibility on the web has been a huge topic for years and serving obfuscated HTML that only works for seeing users goes against everything we have been fighting for.

Yeah, because fuck accessibility, right?

The sad thing is that at least here in Germany they are becoming the only option for more and more products. Most of the things I ordered in the last few years I couldn’t have gotten locally. Often my only other option is a different soulless and ethically questionable online retailer that asks a 30% higher price, uses the worst delivery service in the country and is just as much of a threat to family owned stores.

This mainly applies to movies on DVD and BluRay but I even had to order some semi-exotic cooking ingredients from Amazon because nobody in my medium sized city has them in stock.