Because people don't understand ratios? I use 1280x960 too, because that's a 4:3 pixel ratio and my screen's physical width to height ratio is also 4:3. I don't get why we have 1280x1024 as a native resolution so much... 
1280x1024 does look like garbage on a 4:3 CRT, but some of the 1280x1024 users here probably have 17-19" LCDs for which that resolution is in fact correct.
That resolution has become common over 1280x960 because it was at one time the largest resolution that could fit into the 1MB framebuffers on video cards.

Well no worries. I just did my opening credit subtitles so that's 30 lines of text that should look decent on 1280 and a bit off centre on anything higher or lower.
If the text size doesn't scale, the text would still be unreadable on monitors with high pixel densities. It has been a while since I last tried out any subtitles though.