Features of Windows 7 and Windows 8 won't users see in Windows 10:

• DirectX 12 is included in Windows 10, and it is a must-have for serious gamers. Initial sources stated that DX12 will improve performance by 30-40% over DX11, and while the truth is closer to 10-20%, it's still a lot of money for old rope. DX12 will never be available on Windows 7 or Windows 8.
• Search / Cortana – While Windows 8 has a decent online search built into its divisive Start Screen, and Windows 7 just has local searches (what's on the computer), Windows 10 clearly outperforms both.
• While both Windows 7 and Windows 8 do a decent job of keeping users safe, Windows 10 takes the game to the next level with a number of additional features. The first is 'Device Guard,' which protects against zero-day attacks by validating unsigned software and apps.
• Windows 10 is still very new, and it includes a startling number of flaws that you won't find in Windows 7 or Windows 8. Disappearing icons from the taskbar, Start Menu lock-ups, Windows Store download glitches, copy and paste failures, audio issues, and other issues are among them.

Read More: What is your review on newly launched Windows 11?