The difference between the SW screw profile and the real screw profile

Hello everyone,

I got a question about the screw which is created from the SW toolbox. With the SW screw, the profile was created from revolving the sketch. With the real screw, they have a helix profile. I attached 2 fotos to let you see what the difference is. So could you please explain why does the SW create that profile.

P/s: sorry, english is not my first language

Thanks for your answer.

SolidworksToolbox