With Matlab, yes it is just tabular data that is being read in using xlsread, but when you have existing scripts that are based around that function it can be difficult to get people to try something else. As for the others, VBA macros are used in various missions to get things done.
This sort of gets to the point that real or not, there is a perceived risk that moving to a new, open source solution will break things to a greater degree than the usual upgrade cycle of MS will. It really is vender lock-in, but it's so pervasive that to break it you do have to work with more than just the other parts of the office suite.
Just in case anyone things I'm an MS shill, I'd love to have an open source alternative (I'm a poor college student), but right now, I am locked into MS Office.