Spikes doesn't seem very appealing. An offensive spikes user is good when it forces a lot of switches, and, it has a fair number of counters that would make boosting/attacking fruitless until these threats are removed, this lets that pokemon act very effectively early game when these counters are healthy. I think a decent example of this is spikes gren, thought seldom used, it can be pretty decent against teams with Chansey, as youll really fail to do much damage as you force the opponent's Gliscor or Hippo out, but, if you drop some spikes on that turn, then you're starting to chip away at the opponent even if they wall you. SR terrakion isn't dissimilar if the opp has Lando / Gliscor / Hippo.
I really can't think of many situations wheres this is true of diggersby.. Skarmory carries defog. I think you beat Lando, Venu, Hippo, Mandi, Physical wall if you SD as they come in, so thats basically moot. Most offensive switch ins eat shit if you hit them with the right attack. Diggy is actually that strong.