Yes, but what should be in the alt text for the image? Your pie chart example makes sense (“pie chart showing fraction of lemurs (40) and cows (60)”) because there are only two data points, but what should it say for a line chart showing the GDP yearly since 1900? A huge list of numbers? An overall interpretation of some sort?
It would be context dependent. For automatically-generated alt-text you’d likely see some human-understandable representation of the text which would likely be something like, “… 1919 GDP up to 4 million, 1920 GDP down to 3.9 million, …” On my own personal site when I’ve presented charts, I usually give an overall interpretation of the data, see, e.g., https://www.dahosek.com/2023-in-rejections-and-acceptances/ or https://www.dahosek.com/writerly-resolutions-november-status... (I just realized, looking at these pages that I need to do some fiddling with WP templates to get rid of the big ugly display of the featured image at the top of the page which doesn’t include any alt text at all). But the point is that just throwing unlabeled numbers at the user is not an acceptable presentation for accessibility.
(since I posted this, I’ve done some clean-up, although I also noticed that MarsEdit likes to put meaningless stuff into the “title” param of the img tag)