good question - it depends. When I started out, I never did. I went through about a dozen different epoxies since I started this, and they all were great when gluing wood to wood, stabilized or not. So, in that case I don't use dovetails because the bond is so strong that I have no concerns about them.
But I always had problems when using metal spacers: When sanding the glued handles, the thin metal spacers would heat up in seconds, and the epoxy bond would come apart because most are only heat stable up to about 200F. Because of that, I have started using not dovetails but little dowels inside the handles when I use metal spacers, and occasionally also with other spacers that can be a bit brittle. I haven't gotten around to drawing it up, but basically, I predrill the handle piece with a thinner drill, 3 holes next to each other then turn into a slot for the tang. Then I drill a wider hole 1/" - 1/2" into the handle and into the ferrule and connect them with a softwood dowel. If I use a spacer, I drill it with the same diameter and just slip it over the dowel. All this does take quite a bit more time (which is why I have slightly raised the prices for handles with metal pieces), but it is very stable. I have tried to intentionally break one of those handles and couldn't do it with reasonable force.
I hope that answers your question,