It's to prevent wear and damage to the anodizing on the chair's axle tube. The lift is designed to be very generic and so it's not really an incompatibility thing. The lift is intended to pick the chair up by the 19mm aluminum cross tube on the backrest but that's not a real strong part to hang the entire weight of the chair from, especially on rough roads. I designed and printed some hooks to lift and support the weight of the chair by the axle tube. In the picture here https://flic.kr/p/2peh56W, there's some white foam tape that was used temporarily. It's not very durable, though.