What kinds of professional applications are you thinking of? Like something meant for health care, finance, construction, education, energy, telecommunication, real estate, manufacturing and other sectors?

It makes more financial sense to write software for the most popular OS, not a minority OS. When a company makes software like that, they expect to sell it to only very few customers who are willing to pay hefty sums for it. Targeting a market segment with 100 potential customers sounds more appealing than targeting a market with only 1.

However, in a market already dominated by Linux, such as servers, clusters and mainframes, the tables are turned. When most of your clients already use Linux, it makes more sense to write professional applications for it.