Boards are required, and there are different kinds of board members, some of them are are appointed and/or voted in by shareholders. So it's not exactly a question of being "deserving". While Microsoft is probably going to have some sway, this process is not necessarily about Microsoft picking people to guide their development strategy, or picking people who are in their best interests. This is sometimes shareholders putting in people who can (among other things) - 1) oversee the corporate governance, make sure the company is playing fair with their stock, 2) put in people who are successful and can guide the company toward business success, 3) create a network for hiring & replacing executives when they leave for any reason. That said, having diverse input from other large businesses seems like it's always going to be an advantage.

They can also represent the enterprise software needs for those industries.

As a software giant Microsoft's products intersect most parts of most economies. A hotel chain has its own technology needs and has views of the technology needs of its customers.

Whether a high-placed member of Marriott has specific insights to Microsoft I don't know, but I don't think it takes much imagination to fill in hypothetical reasons the person could be helpful.