Why Are T-Slot Extrusions the Most Popular in Industrial Framing?

T-Slot Aluminium Extrusion - 30x30mm PG30 Profile aluminum t slot extrusion T-slot structural framing is a framing system consisting of lengths of square or rectangular extruded aluminium, typically 6105-T5 aluminium alloy, aluminum t slot channel T-slot use creates a pivot in the assembly Brackets are able to move around because of the clearance in the bolt hole Tightening the component

aluminum extrusions t slot My question is - why use expensive extruded aluminum T-slot? I mean, for a CNC router it makes sense because you need sub-millimeter