So many products need access to your network stream to avoid installing much or any software on the servers and such. The problem is that a lot of switches especially Cisco can't do too many spans per chassis. You can use taps, which is good, but not if you need many of them to instrument a switch. This creates a big problem that some vendors are trying to solve with specialized devices.
The problem with other large companies, such as mine is that we can't buy systems from small companies (well not easily). I know some companies are using products like Toplayer's IDS Balancer to do layer 7 span traffic routing. There are other players like Netoptics Maxtrix line, that makes a hardware switch. I don't know of anyone who is using these.