If you always default to launching on iOS, don't be surprised if user adoption is further limited when you eventually get around to launching on Android since by then, there would be competing products or you'll have difficulty changing the perception of "this company thinks I'm a 2nd class citizen, why would I bother?"

(Snap faced some of this for a while though I'm not sure what their distribution metrics look like now)

There is also a critical window when launching on multiple platforms. If you wait too long, the brand's "xyz OS only" will stick and opens the door for your competitor to say "We're like that other app but we actually work and sync across all your devices".