That's always the argument from the business standpoint. How much of their ecosystem is on a foundation of professional Mac users? A majority of the professionals I know won't buy the current touchbar model MacBook Pro. Does that market even matter anymore?
I would think a company with the resources Apple has would be willing to invest more in loss leaders that keep users fully in the Apple ecosystem, or in products which may contribute in small ways to their bottom line, like Macs. They can afford to make their primary metric market share, rather than profit.
iOS can't replace Mac OS (yet) for serious work. So instead of letting Macs atrophy, they should invest in making Macs the best possible desktop and laptop computers for serious work. Own whatever amount of that market they can. Keep those users in the Apple ecosystem.