Probably 10–15 times. And usually about 10–15 minutes into the pitch / meeting.
Generally, this only happens in a pitch that was a cold intro, or a “favor” meeting. Otherwise, generally you can screen out the folks who are unprepared ahead of time just looking at their deck and materials.
But sometimes, you take a meeting, and after 5–10 minutes, as nice as the founder may be, it’s clear they just don’t have whatever product, metrics, or vision is necessary to be a fit. Or they just aren’t remotely prepared for what it takes to discuss an investment.
It’s usually not their fault. They just aren’t prepared enough.
I apologize, and explain to them the honest 5 reasons why they aren’t quite ready for what I need to see, and end the meeting. And tell them to email me back once they are ready.
They usually find it abrupt, but later appreciate it.
But I’ve never had this happen in a meeting I “electively” took. Only when it was one I reluctantly took, a favor meeting.
So I try not to do those anymore. They aren’t really a favor to anyone.