It's not nefarious on the part of the _developers_. They were given concrete goals. I wasn't privy to those, but it sure looks like those were: Must work in Chrome (Android) and on iOS, working elsewhere is nice to have but optional. They were also given deadlines. Then they proceeded, with no nefariousness, to deliver a product that works on Chrome and iOS and not elsewhere. I'm sure if they had more time or more people they would have made it work elsewhere too.

Then you ask yourself why the goals were set the way they were. Obvious guess at an answer: because they only want to target "mobile" and Android+iOS cover most "mobile" clients. Had iOS had less market share, I will bet the goal would have been Android-only (modulo advice by lawyers based on antitrust worries in that situation, of course).

No malice anywhere along here, but the end result is not so distinguishable from malice, sadly.