Here’s the raw truth, as I understand it. I’m one of the people who has used this phrase. Typically I pull it out when I absolutely lack the ability to explain and verbalize something in a way that the intended audience can understand and accept. Yes, it’s a failing on my part, but also, despite what everyone wants to believe, not everything can be distilled down to a simple easily understandable explanation without losing the message. You’ll probably understand when you get older.

Realistically, it’s not so much a guarantee that you’ll understand the exact nature of what I’m saying when you’re older. It’s more that when you’re older, you’re probably going to be more willing to accept that I have my own perfectly valid reasons, even if I can’t articulate them effectively, that the world is complicated, and sometimes it’s those complicated and difficult to articulate threads that are actually the only things holding everything together. So, when I say you’ll understand when you’re older, I might not mean that in the most literal sense, it’s very likely that I’m speaking more in a metaphorical way.