Why? Because you're not a plumber/ carpenter/bathroom fitter?
Serious question, I can't see in the pictures why it couldn't come out. Surely it would have saved so much time and stress even if it was, for some strange reason, awkward to remove.
.....Good morning!
Yes good morning Paul!......
And as you were so polite as to ask nicely, I'll answer you.
The builder in his infinite wisdom thought that the unit and sink were so heavy that he first bolted the carcass to the wall, adding extra cross members at the back and Chem fixing the bolts in, issue 1.
Then........ he placed in the sink, and proceeded to chem fix in two more bolts thro openings in the back of the sink. Even with the nuts undone, the sink won't pull forward enough to clear the bolts to enable you to lift the sink up and out.
Is that a satisfactory answer for you?