Patch and maintenance should never happen towards the end of the week. If there are any issues that require additional emergency maintenance, or for adjustments to be made after the patch goes live then it can be sticky when everyone is on their weekend instead of trying to rush and call people in. Not all places conform to this but it is general good practice to allow for ample time for issues to get ironed out.
Besides, having it on a Monday just gives ample time for any adjustments or further maintenance to happen.
Look on the bright side the next time July 4th will fall on maintenance will be, what? 2033?