I've had it happen both ways -- an LAX-EWR flight held for several of us on a weather-delayed inbound RJ -- in my case it was to an international connection in EWR, and any alternative would have been at least a day+ later arrival. Another time there were 8 people on a mechanical-delayed inbound connecting in DEN -- the door closed 2 minutes before we arrived at the gate...10 minutes early (yes, I know they can do that). It wasn't oversold either, it went out with 20+ empty seats and arrived 20 minutes early. It wasn't the last connection, but the next flights were 4 and 8 hour later, with the 4 hours later being a full RJ that 3 of us barely made it on standby at the last second.

It seems like UA has heavily banked the flights these days leading to potentially more misconnects -- got flights for a transcon college visit with my daughter, and everything was either 50,55, 59 minute connections or 3.5-5 hours. And the longer ones weren't good for various reasons, so picked a 59 minute IAD connection, will see how that goes.