Does Discovery Call really work?

Recently, I have been reviewing a bunch of SaaS tools and it seems like the discovery call which is separate from the actual demo has become the new normal. This must be done as an initial step- but what do you think about having this conversation over phone? Often, unscheduled one? I found myself getting frustrated with being caught in between errands and grilled about what other tools I have been testing and bunch of other insights useful for them and then being left with nothing for over a week before getting an actual demo. Does this really help with getting more deals closed?