Why are text-objects text objects, and why can they not be calculated like mesh objects? Why is Blender not able to calculate text-objects like mesh objects? If there is a way to completely edit a text-object as a mesh, but keep it a text, or some add-on to do the same thing, could you please tell me?
It has to do with specific font properties.
And also copyright rights :).
Modern computer fonts don't have fixed proportions like meshes do.
They're ever so slightly adjusted when you scale them up/down, to look optically correct.
In low resolutions, they also take advantage of hinting data, to avoid pixel distortion.
Good fonts also contain kerning data. This tells them how much space to put between different character pairs. And allows for ligatures.
When you convert text to mesh/rasterize it, it loses all of these important features.
That's why some font creators explicitly prohibit rasterizing.
What you are asking for doesn't sound possible, a text object is based off the type face you are using if you want to edit it, it'll will have to be converted into a curve or mesh. If you want to keep as a text object and still be able to manipulate it some how you can still apply modifiers to it or mess around with the Geometry settings in the object data tab.