Think of it the other way around: why are you drafting in something called "Model space"?
When I first learned CAD formally, it was mostly for the utility of paperspace in AutoCAD, TC only had one paperspace in those days. Our drawings had to be produced for plotting/printing in multiple sheet sizes, so we set up multiple paperspaces for multiple sheet sizes of the same sheets. They looked the same at a glance, but had different line thicknesses so that if they were scaled by Xeroxing/photocopying, say A3 reduced to A4, finer lines and dimensions or notes weren't lost or blurred into others from printer/plotter/copier resolution inadequacies. The lineweights are the the thickness of drawing pencils and pens: 0.3mm, 0.5mm, 0.7mm, 0,9mm, 1.3mm, something of a legacy from manual drafting. Laying out multiple copies of the same sheet with the differing line weights within model space itself is a dog's breakfast. Have you noted what happens if you zoom out in model space with different lineweights there? Alternatively, you have multiple copies of the file, with the possibility for confusion and error that that introduces. Different lineweights for different sheet sizes is an ISO standard, so compliance is necessary for ISO certification, a requisite to do business with many companies and all government agencies here in Australia, other countries as well.
Those are the old school reasons, and it's the reason why even 2D CAD programs separate model space and paperspace. In 3D, paperspace and TC Pro's Drafting Palette do most of the drafting and documentation of models for you automatically. Students learn CAD modelling, not technical drawing. Modelling a subject gives you the capacity to compute its physical properties, it allows you to assemble things virtually and establish relationships, sizes and interferences at full size instead of introducing error from scaling. It can give you access to inverse kinematics animation and rigging, rendering, 3D printing and rapid prototyping, and data exchange for CNC mechanisation. Drafting as a profession is going the way of secretaries with WordPerfect or Wang word processing certification.