[TeMPOraL]

Big companies are often are complicated mess, and I can emphasize with desire to simplify and streamline operation. There's some benefit with setting your infrastructure in such a way that there's a known party you can pay to fix things quickly, and that you can sue if they can't.

[AndyNemmity]

Often they also like to stay understaffed in IT, so having consistent vendors, and similar systems allows them to keep just a few guys around that have any clue how it works, and supplement with consultants and vendor support.