I wish they had an Android app. Hopefully, it's in the works, because I would definitely try it out.
In this case the obvious, though maybe not correct, inference is that their customer is the order execution companies that they are selling their order flow to. If that is the case, it is in robinhoods best interest to make that order flow as "dumb" as possible such that it doesn't make order volume go down.
It might be that it is a tactical decision not to provide high fidelity trading interfaces (via the web or otherwise) because those make their product (you) less valuable to their customer (the order routers).
Again, purely speculation, but it seems a reasonable hypothesis.