There are more "left-wing" people in the world than "right wing" people, for starters, so it's a bigger pool of customers.

Secondly, if you are against, say, gay marriage, you've just potentially lost the entire gay community (aside from dope grifters like Dave Rubin, of course). That's at least 3.5% of the US population (12.25 million potential customers in the US alone).

Also, it depends on the Corp. If we're talking about Starbucks, for example, there is a bigger market in, New York City, than Backwater Falls, Kentucky. New York is a "left wing" population.

But while Starbucks perhaps puts a pride flag on their Twitter bio, they are also engaged in a huge union-busting campaign right now. So the real answer is that corporations are not left-wing. It's a lie (er...marketing, I mean, of course).