patrick, if you haven't noted, firefox and chrome are cross-platform tools. perhaps you mean the number of people who use those tools on linux ... if so, here are some numbers from ardour.org:

Rank Requests Pages OS
1       1064670 50842   Windows 
2       1008038  23804   Unix 
         1001554  23713   Linux 
         5482               77  BSD 
         696                 10  Other Unix 
         306                   4  SunOS
3       3106311     5647  OS unknown
4       476795    14399   Macintosh
5       51448         8052  Known robots
6       14                   14  OS/2
7       1862               11   Symbian OS
 
if you were to use this, you'd note that even on a site about a DAW that doesn't run on Windows, (apparent) Windows users outnumber Linux users by more than 2:1. of course, this statistic has all kinds of flaws and caveats, but the point is that the data that is available to companies such as NI strongly argues against supporting Linux. if you have real data that would convince such companies that their existing decisions are wrong, then please do share it.

for the N-th time, open source is *not* Linux. Audacity is popular because it is a powerful, useful, cross-platform tool. Linux has (probably) very little to do with it.