There is one reason you should choose to stick to one platform (whichever one it is that you choose).
For example, unless you happen to be as well-versed in developing for iOS as you are Android (you aren’t), you are now paying to develop for two wildly separate platforms that you have to keep at parity*.
You’re now spending *twice* the dollars to develop the same feature (and even more to support). That means you’re twice as far (at any point) from developing the ideal product/market fit. Are you willing to risk your business that you’re going to get twice the growth, equally, to pay for that choice?
*Not having an Android app means sad users that are bummed they’ve bought a platform that many leading developers don’t cater to. BUT(!) Building an app that doesn’t have parity/is crappy will absolutely enrage your users and make them feel like second class citizens.
E.g. “No I’m sorry. You have to have a membership to come in this club” is not the same as, “Sure, you can come in and watch those folks up there drink champagne and eat oysters, whilst you’re down in this pit drinking Coors Lite. That sound good?”