Why does the rainfly by the doors not come completely down along with the rest of the fly?

Tech Specs:

Material:

[Fly] 75D nylon; [Floor] 1800mm nylon 

Freestanding:

Yes 

Poles:

2 

Pole Material:

DAC Featherlite NSL 

Doors:

2 

Clip / Sleeve:

Clip 

Floor Space:

92 x 79in (234 x 201cm), 45sq ft (4.2sq m) 

Interior Height:

43in (109cm) 

Vestibule Space:

9.4sq ft (0.87sq m) each 

Packed Size:

22 x 8in (56 x 20cm) 

Seam Sealed:

Yes 

Ventilation:

Mesh walls 

Weight:

5lb 11oz (2600g) 

Recommended Use:

Camping 

Manufacturer Warranty:

1 Year 

Country of Origin:

China