According to a recent study (2017), for the US market, Windows computers have 38% of the market and Apple 9%. Since most of TurboTax sales are for personal software, the Mac market for business software is just not there to justify development, production costs and continuing support.
Perhaps, if and when Apple computers are at least 25% or more of the US market it will be different.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
