Learning + checking the bitcoin address creation process at each step
Any program actually generating bitcoin addresses will always be hashing the bytes directly - what you see on the Wiki are simple hexadecimal strings representing those bytes.

The various hashing sites you have tried will treat those inputs as strings. For example, instead of hashing the byte 0xFF when you enter FF, they will hash the text FF, which is actually two bytes if interpreted as ASCII. You will never get a correct answer using such sites.