Pattern unlock required when starting phone AFAIK on Android 7 Nougat, when you set pattern unlock, the user is not required to enter the pattern to power up the phone. However, on Android 8.1 Oreo (I'm running a Wiko VIEW MAX Android 8.1 phone), you cannot power up the phone unless you enter the pattern. Why was this feature introduced in Oreo?

Why require it? After all, once the bootup is complete you will have to enter the pattern again to unlock the phone.

Thanks.
Simply put... 


  Android Oreo - 8.0 uses Forced Encryption


The data is now encrypted for safer usage on Android, older devices had the option to encrypt in security settings.   



Nowadays it is a requirement of Android to safely protect your data. 

Why is so important ?
Encryption helps to stop personal information theft fron even the most persistent malware and spyware.

If the device was compromised at a kernal level, your sensitive information could be leaked via USB prior to the device ever being started... 

Due to significant amounts of custom ROMs with vulnerable kernals and custom recovery programs, most information can be extracted using the recovery program or othe means like pre-boot software and even CPU EMMC Storage access using USB Cables ..

SP Flash Tool's Read Back function is a great example of an extraction method that can access your unencrypted private information without ever needing to even have a battery in the device... 

Once the unencrypted DATA partition is extracted your information like the Passcode used for Unlocking can be easily extracted...

Using the annoyiy Double Unlock method seems more of a burden than anything i agree, however it is a much needed level of protection.  

Encryption will not help with Online security as some people think, because Android uses the first Unlock screen to Unencrypt the Data partition.. The fact is you still run on an Unencrypted device, however the Data partition is encrypted Prior to Boot.. . 

I hope that clears everything up...