Coming from the silicon IC design industry, there are huge IC layout tools which run exclusively on Linux. They work a lot similar to AutoCAD-like software - they do a lot of automatic layout, place-and-route, 3D design, etc.
These tools run for weeks at a time on linux machines and are highly optimized for Linux.
That existing market could have been so easily translated into software like Autocad for Linux. But something went wrong somewhere - probably the OS graphics API was not good enough (a frequent enough complaint for Linux)... I really dont know what.
But even after a proven 4.4 billion dollar market (EDA industry market cap) for Linux based high-performance design tools, Autocad went after Mac. Knowing fully well that TCO for a Linux based system is far, far lower than a Mac based.
On the other hand Maya already runs on Linux and Mac OS X. So they may be using Maya numbers to calculate sales and difficulty porting. Since it's used for video work you'd expect more Mac sales.
I think stability is not the main reason - it may be perceived market or the graphics API problems that I was talking about (especially with third party drivers - nvidia and ati)