I would say it's a soft requirement in most cases. One must be prepared for an extra uphill battle trying to secure a job without one. As someone who just broke into the industry this month (with no degree), my biggest assets were an existing portfolio of work and leveraging my ten years of professional experience working on complex/critical problems in various fields.

I don't think this is strictly related to software engineering, though. I think most people doing horizontal career transfers use some form of the above to achieve success.