I don't think this practice is in Microsoft's interest. People who buy a PC with FreeDOS usually install a pirated copy of Windows (or Linux, but not sure what the exact proportion of those is), which definitely doesn't contribute to M$'s bottom line...
Microsoft is the reason why this practice exists in the first place. Their Windows distribution contracts with OEMs say that all computers that an OEM ships must be preloaded with an OS (likely for the piracy issue you mention). Shipping FreeDOS allows OEMs to sell computers to people who don't want to pay for Windows licenses while also not having to provide support for Linux (or some other alternative OS).
On the contrary, being the primary desktop OS that everyone uses and thus everyone supports is Windows' biggest advantage. Anything that helps thingns stays that way contributes to Microsofts bottom line.
