An ASP lessens law firm control over the outsourced process. An ASP also is a monthly cash drain. Like cable television, the bills may not seem like much at the time but they add up. I will never forget several years ago an executive of one of the regional Bell companies asked me how it could make money on the Internet. It was obvious the company recognized the Net as extremely important to the future, but had no clue how to exploit it commercially.
ASPs solve that problem for software vendors.
Maybe software vendors need to realize they may no longer be in programming. Instead, they are in the service business. In fact, there is an established legal software vendor that continues selling its old proprietary program, but its ASP version is only a half step removed from that model. You must use a special Web browser to input data, but only through the vendor's server, not yours. After all, a new vendor could argue that its expertise is the ASP, and it is not going to waste resources writing a desktop program to sell outright.