So close but…
Emulation. When you absolutely, positively had to run Windows. Possibly a networking issue, but maybe there was an app you needed to run. Most likely you just didn’t bother to find out if there actually was a Mac version, and did you contact the company? Unlikely.
Now the funny thing that happened here was that Virtual PC, formerly the #1, got bought by Microsoft, made into a PC version and now given away for free! but only on that platform. Current #1 would therefore have to be Parallels.