Because someone will sue you, and you'll be forced to pay it.
Musicians are petrified of their songs being leaked to the Internet, so a lot of them store demos or completed songs solely on their personal devices — phones, computers etc. This presented a problem for singer/songwriter/rapper Ryan Leslie, who had his laptop stolen while he was on tour in Cologne, Germany in Nov. 2010. In order to get his laptop back, Leslie first offered $20,000 but then soon increased the offer to $1 million. What a terrible negotiator (with himself)! Here's the short video where he makes the $1 million offer, in writing no less.
So, naturally, a German guy named Armin Augstein found the laptop and soon heard of the $1 million reward. Leslie was all, "Hahaha, sure, one million dollars, yep," but Augstein was like, "No, seriously, you owe me a million dollars," and sued him in Manhattan federal court like any person would after being told they'd get a million bucks simply for stumbling upon some random laptop.
Well, yesterday a jury decided in favor of Augstein, meaning Leslie will have to pay him the full reward. Also, Ryan Leslie has a million dollars to spend apparently, which is a lot of money for someone who once wrote a Cassie song. (Amazing song, OBVIOUSLY, but still.)
So, there you have it. Next time you lose something, don't offer to pay someone $1 million dollars for it. A nice crisp $20 usually suffices, if not, go from there in small increments until you and the other party can come to an agreement. And if you're a millionaire musician, store your music in various places so that you can just buy a new laptop instead of forking over a million bucks!