>many companies don't allow you to use code with the unlicense because of its unclear legal status

I'd argue that this is an advantage of "funny" licenses: any megacorp can use your MIT code without giving you anything in return; if the same corporation really wants to use your funny-licensed project while being legally in the clear, they are now incentivised to approach you, potentially offering some compensation for a more "serious" license.

At the same time, funny licenses don't stop enthusiasts from working together, and that's what makes open source software good.