>> Well it's a net negative for the end user, which should have been the priority for everyone involved
I feel like you're missing the point. Let's say you are a product manager. Here are your options;
A) increase the product price so the budget can be bigger. Understand that increasing the price will lower customer numbers, but net inflows may be larger. (does this option prioritise the end user?)
B) spend all your budget on platforms with the most usage. Ignore less-used platforms completely, but deliver the best possible for your selected platforms. So 100% spend on the Windows client - - and of course ignore Apple and Linux desktop. (does this prioritise the end user?)
C) build a cross-platform solution that is sub-optimal on all platforms, but targets multiple platforms on a limited budget. This reaches the most people, but the experience from an engineering point of view is less than ideal for all of them. (does this prioritise the end user?)
How you answer depends on who you consider the end user to be.
If you see them as "people who have bought our system on our preferred platform" then option B makes the most sense.
If you see them as "people who could use our system to improve their lives" then option C makes the most senses.
If you see them as people who can afford fine engineering then go with option A.
On the up side, no matter which one you choose you are prioritising the end user, so it fulfills your premise.