They do not worship the beast or recieve its mark,but that isn't why they are put to death.
,die for thier testimony of Christ.
Their testimony is about serving Christ , and since they worship Christ they refuse to worship the beast , they die because they refuse to worship the beast ,
You need to get a better grasp on the topic overall , it is not about men and what men want to do ..
The beast , the false prophet and the image of the beast are like an unholy trinity - they are all the same team , this topic is about satan vs God as it goes way back to when lucifer said he would be the most high and convince 1/3 of the angels to join in a mutiny of sorts, God took Eden away from lucifer and gave it to Adam, then satan tricked Adam into sinning
What Revelation is about is the showdown between Jesus and satan which we Know Jesus wins -it is not about human men, God just utilizes men for His own purpose , the beast is revealed to be under satanic power as well ad the false prophet which is why they are thrown Alive directly into the lake of fire , not killed like ordinary men -the beast and false prophet are not going to the great white throne judgment , they go directly ALIVE into the lake of fire
until you really understand what it is about you will struggle with this
there is much about this topic you do not understand , and I am not going into the time it takes to explain it , Douggg may , Revealing Times may , and there are others here that may , but it takes more time than I can give it
sorry but you need to learn why there is a first beast , a second beast , and the image of the beast
I have told you that it is not about buying or selling , it is not about you die if you don't get the mark - it is about WHO YOU WILL SERVE
Your soul will be given up if you accept the mark
because accepting the mark is acknowledging that you will worship the beast
And if you do not worship the beast you will be killed
you are taking that verse and ripping it entirely out of it's context and trying to make it stand on it's own which is why you fail to understand this topic