Patent fun: Microsoft Word sales banned in the US

Also things like patent portfolios and whatnot are considured assests and often can make it easier to get loans and other favoriable deals for investors.

If you think about it a large amount of patents lowers the risk to investors if company goes under. Those patents don't evaporate and when the company goes into bankrupcy then those patents can be sold to other companies and get some money back for the investors.

The USA software patent situation were to change then the perceived value of many large corporations could be affected quite negatively.

In fact this is probably how many patent trolls get started... A software company goes under and then sells off their patents to wealthy lawyers. Then those lawyers form limited liability corporations to those patents and start trolling with them.