Pro Tools is a special case as they used DSP farms on plugin cards to make up for the lack of fire power in the cpu. They were doing huge things with these DSP farms back in the 486 days. The big reason they are every where is that for many years they were the only game in town. Native DAWs just didn't have enough fire power to compete with the DSP farm till fairly recently. With out the DSP farms the software was effectively useless until they brought out the LE version but, those were still tied to specific Hardware read "stuff they made and sold". It wasn't until last year when they brought out Protools 9 that you had a version that wasn't tied to specific hardware. Protools is still the most common in Recording Studios but, Logic, Cubase/Nuendo, and Digital Performer are pretty common as well. In fact Nuendo is the preferred software for motion picture and live recording. Personally, I don't care for Protools. I have it at my studio but, I usually use Nuendo. When a client brings in a Protools session, I usually use my copy of Protools to make it easier to export the session to Nuendo and to import it back to Protools if they need it. I think of Protools like I think of Word. Just because its in a lot of places doesn't mean its the best tool to use. It's only one of the most common.