I'm not understanding why if I've bought sats that I can't immediately send sats. 

I want to practice spend and replace. If I can't do that for a bunch of smaller (let's say sub-$100) purchases, then it's really hard to justify using strike as a platform for anything other than efficient DCA. In that regard, it's as good as it can be given the onerous KYC requirements. (I'm not blaming you for those, just to be clear.)