The Supreme Court is expected to take up same-sex marriage in March, and the business community has something to say about it. Yesterday, more than 200 employers signed onto a “friend of the court” brief making the business case for marriage equality. Today lawyers are expected to file a similar brief.

If you scan down the list of companies signing on to the documents, one industry stands out: Tech — big deal tech, like Apple, Facebook and eBay.

So, why do it?

“I think it’s a mix of idealism and pragmatism,” says Stanford law professor Jane Schacter. Idealism, she says, in that a lot of these companies support marriage equality, plain and simple. And, says Schacter, “I think on the pragmatic side, they’ve made the calculation that for a number of reasons this is actually good for their business.”

One reason, companies in states like California — that don’t allow same sex marriage — are at risk of losing employees to states that do.

But it’s also a reflection of how much things have changed culturally.

“Opinion has shifted enough in the last couple of years that they are more worried alienating people by not taking a position than they are by taking a position,” says Harvard professor Michael Klarman.

But whether or not it matters to the court, we’ll have to wait and see.