The question is why I am not being asked if I want to change the photo size?
Well, maybe, probably, that's just not a feature of your email app? Maybe your email app doesn't recognize that it's a
photo that you're sending. As opposed to any other of hundreds of thousands of kinds and types of files possible. In geek speak email apps are file type agnostic, afaik. Designed to be.
OTOH, if it's e.g. super hardcore porn and your carrier cooperates with a moralistic big brother – what do
you think? – then it could simply be a crude, 'leaky' censorship filter doing a bad job by betraying its presence and activity...
In short, at this point,
anything is still possibly a cause for your distress. We have to rule possibilities out based on
your input,
your information about the situation. Which hasn't exactly been comprehensive, sofar, as srkmagnus already spotted.