This trend is nothing new. We've seen this happen in other special-purpose devices, such as the common router. Routers started as network daemons in Unix boxes and evolved into the Cisco, Bay and Ascend routing products that we rely on and use every day.
Firewalls are no different.
In the past, if you wanted to install a firewall you had to purchase the software, sometimes the underlying operating system, and also a co mputer on which to run it all. It was no surprise that just to get a single firewall in place, it would run into the tens of thousands of dollars. Cost simply got in the way. And cost wasn't even the biggest concern if you weren't fully confident that your setup was providing adequate security. These firewall appliances are specifically designed to do one thing-and they do it very well.