Back in the '90s Bill Gates was worried what would happen if they had a catastrophic loss of business (good protions of Windows, as well as Mac, software was based on other peoples ideas and both companies had to pay off a number of lawsuits back then. Also the DOJ was saber rattling about anti-trust lawsuit). I think Gates wanted enough cash (liquid assets) on hand that he could make payroll for 18 months with no sales. I believe he figured they could re-invent themselves, if necessary. Evidently Apple has the same idea.
WARNING: WAR STORY
Back in the '80s I worked for Dr An Wang. He invented Random Access Memory (RAM) as we know. He also held the patent on the SIMM connector/design that most memory chips use to rely on. Wang Labs also basically invented the "desktop" paradigm that every Windows and Mac user is now so familiar with. It was called "Wang Information System". Problem was it ran on proprietary hardware (IBM based micro-buss architecture). I don't know about Apple but Microsoft paid millions to Wang out of court. Problem was Wang settled for too little (both in dollars and recognition) because they were going out of business and didn't have deep enough pockets for a protracted court fight.