Very few mics are designed with concert tapers in mind. Maybe Chris Church and Jon, but that's about it. The rest are designed for studio or stage, typically close micing. Out of the bazillion mics out there, a relatively small number just happen to work well for taping a room full of blasting PA at a distance. Before everyone had portable decks with phantom powering, that number was probably smaller than it is today... and most of those from that era have fallen by the wayside, with Naks and Senns being a couple of "the survivors". Fast forward to today where phantom power is readily available. A new set of 421's costs about $750. For our purpose there are a lot of condensers out at least as good for that same money, so that's what most people go for. Now that most of those "old school" 421's are 20+ years old, the ravages of time has caught up with a lot of them, and if a good used 421 goes to Ebay, they are more highly prized by studio folks than they are by us.
One of our locals (Bill Dix) has been running 421's for years, directly into a D8, then into an R09. Last year he decided to buy all "modern" gear. He said he thought maybe the ravages of time was catching up with the 421's, but I think it was mainly because the rest of us a shiny new toys and he wanted some too.