Q: why iphone 6 and 6s freeze?

Try to reset your device. This won't delete your data stored on this device.

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.

Alternatively, you may go to Settings - General - Reset - Reset All Settings

If this does not help, restore your device to factory settings. Note that this will erase the data from your device.

Take a look this Apple Support article: Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support.

no one has answered that question, i have the same issue since 9.2.1

The iPhone has a multi tasking operating system (OS). It is likely that a bug in this OS code is causing the phone to stop recognizing screen touches or it disables the screen input. Reseting the iPhone will allow the operating system to restart and run until it gets in this condition again. You should stay current in your updates and hopefully this issue will be resolved.

It is also possible your iPhone has a bad memory cell or a touch screen which would cause a lock up or freezing.

Reducing the number of pictures and email stored on your phone may help by reducing the amount of memory gates and load on the CPU of the iPhone. However since some many people report the same issue it is more likely a software bug.

My phone has been freezing up the last few months. I'm almost at 2 years with my phone.  My phone has been unresponsive, I sometimes can't even type in my passcode to get into my phone.  I have restored it several times.  That will help for a few short weeks.  I have been reading that many others have the same issue.  I believe they have now acknowledged it as, "Touch Disease."  I guess I will have to suffer till I'm able to get my upgrade with my iPhone.