Aluminum T Slots - McMaster-Carr

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

ALUMINUM EXTRUSION SPECIFICATIONS: Elasticity – approximately 10,000,000 lbs sqin Hardness – Webster Model “B” 11-12

aluminum profile t slot Leading T-Slot Aluminum Extrusion Manufacturers A T-slot aluminum extrusion is an aluminum bar that has been shaped, or extruded, into slotted profiles either

aluminum t slot framing 100% Compatibility with All Leading Manufacturers' Fractional and Metric T-Slotted Extrusions Parco T-Slotted Aluminum Extrusion has over 80 aluminum