Extruded T-Slot Bars

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

T-Slot is a framing system composed of extruded aluminum profiles which use the namesake slot as a mounting point for various hardware

extruded aluminum tslot accessories 100% Compatibility with All Leading Manufacturers' Fractional and Metric T-Slotted Extrusions Parco T-Slotted Aluminum Extrusion has over 80 aluminum

extruded aluminum tslot Product Type T-Slot; Profile Type Single; Weight per Unit Length lb-ft; Extrusion Texture Grooved; Material Aluminum 6105-T5; Profile Height 1 in