Why no drivers need after installation Windows 10 ?

Drivers are still required.  However, Windows 10 is smarter then previous Operating Systems.  Windows 10 will find the Drivers it needs and installs them automatically.
Microsoft took a lesson from Linux.

What's happened, my friend, is that Windows has identified what it believes are the correct drivers for your hardware devices.  These MAY or may NOT be the best drivers for those pieces of hardware.  The currently installed drivers MAY not provide the full functionality of each of those devices.  Having said that, if things appear to be working well, just use the drivers that Windows 10 has provided.

Windows 10 will download most driver's automatically. But some gpu will not function on Windows 10 without installing them in comparability mode if you don't know how to install in comparability mode read up on it