Might be some missconfiguration of apt, or some of utilities you use like apt, apt-get, aptitude, wajig, synaptic... as you can configure apt to install recommends/suggest packages by default also or disable just rec or not to install these at all, etc...

Everything is normal, if that is what you want. Requirement of libgimp is there so that suggest works, sort of necessary bloat.

Otherwise rebuild sane/xscanimage without gimp plugin, general purpose binary OSes which target wide audience must serve anybody not just you, so dep bloat is there considered either necessary evil or necessary angel depending on POV

Needing scanimage, I ended with just gimp and more into my configuration.

Might be an issue for some users.... not willing to much add ons. Is this normal?