Professionally, mortars have been around a long time. Not sure about for consumer use but I recall them being around in the early 90s personally.My family never used them but people in our neighborhood did, but I don't recall that being very common either
That's probably why I don't remember seeing them.
Just seems like for the past decade or so the expectation for lighting fireworks is setting off a shit ton of "artillery shells". And it's basically every single fireworks party at this point.
Even when you go to buy fireworks or talk about fireworks people are discussing the cost per shell.