Djay 2 necessary for iphone? And why is it not already included with WeGO4?

My question has probably shook professional heads - I am a complete DJ amateur.

So, I just picked up the Pioneer DDJ-WeGO4. It comes with VirtualDJ 8 & Rekordbox dj.

Since I do not own a laptop, I have to learn to operate the WeGO4 via my iphone, but need to download Djay 2 for my iphone.

It’s not really an issue, but was wondering why I have to pay extra to download Djay 2. Considering VirtualDJ & Rekordbox come included with the WeGO4 (for your PC / Mac), why is there no option to download a free & fully functioning DJ software for one’s iPhone / iPad? Shouldn’t this have been included too?

Again, I’m a newborn when it comes to DJ’ing, and hence, would love some knowledge dropped on me!

Thank you in advance.