For Blacksmith specifically they’re using おっさん in the Japanese at times, which is a more derogatory way of referring to older male character. Which I suppose is why the English has followed suit with something similar.
In many ways it just feels like it’s born from the same societal tropes that plague female-oriented romance series, where once a woman is over the age of 20 (or god forbid approaching 30!), their lives are over and they’re no longer marriage material. Maybe because the writers are on the younger side themselves and just happen to buy into that nonsense or not, I’m not sure. But it is an unfortunate trend all the same!