That’s the problem; nobody wants to wait. They think if they’ve read a homily by Pope Francis, or if they know how to make the Sign of the Cross, they’re ready to be received into the Church, and **if there’s a policy that they get to be received at the moment of demand, then they will receive little if any formation whatsoever **- after all, why take a course or undergo a process of conversion, if you don’t have to?
We used to have that policy of receiving people on demand, and our experience of it was very negative - Father was finding that they were treating him like their servant, and not obeying anything he told them, since they got the idea that they could just demand anything they wanted from him (and naturally so), since they were received into the Church on demand, after all, which is why we have switched back to requiring people to undergo the RCIA.
It’s not perfect, but it’s something, at least, and they come into the Church with at least some idea of the expectations, and some knowledge of the faith.