probably because at nearly every place I've worked at the sysadmin/ops group was the #1 obstacle to getting things done. Sure some of it was "saving you from yourself", but a lot of was pure obstinatance for no other reason than I think sysadmins just cant turn it off anymore... much as your mom says "dont frown your face might get stuck", it appears a lot of people (not just sysadmins, developers too - you know the one, in the corner who is old and surly, been there forever, and hasnt been promoted in about as long).
The deck is stacked against sysadmins - developers are the people who deliver business value to leaders, and sysadmins are the ones who cost money and say 'no'. When you are on a tight timetable, the person who says "sure" is the one who gets the high fives... assuming things work out, of course.