"a genuine question. Why tune up rather than capo?"

Because often you only want to tune up one string not the whole lot.
For example, I mostly use standard G tuning, but frequently up-tune the top D a whole tone to cheat when playing in Em (my favourite key). Only snapped on me once so far and it probably was due a new string anyway. I do use very light gauge strings which probably makes it withstand more re tuning.
I also sometimes up-tune B to a C to play in G modal tuning and have never had a problem.

On the subject of capos - a great 5th string capo is the Woodies G-Band. Does the job perfectly - I couldn't bear to drill into the neck to install a Shubb.