Cost/Hassle of Escrow...
If companies are (rightfully) bothered about retaining access to sourcecode if the original supplier goes bust, why don't they put more pressure on closed source vendors or move more towards open source software?
The vast majority of closed source software bought by businesses has no comeback whatsoever if the original supplier goes bust, and with large companies like banks going bankrupt, and the history of big bankruptcies in the tech industry, you'd be foolish to blindly trust closed source software even from big vendors like MS, Oracle or IBM etc.