but on the other hand if you dry sift plant material aggressively for a long enough duration to remove a vast majority of the resin you can still, with enough pressure and heat. form the sift into a solid form which is better than most commercial hashes. Seriously though, it's not that hard to make better than 99% of commercial hashes out there, more often than not a joint made out of fan leaves is stronger than most hash for sale!
There's full melt, there's hash that will bubble and further down the scale of purity there's hash that will leave lots of ash..but there's another type of hash that not many people are into that is a sort of a cross between bud and hash. You can make it lots of ways, one way is by dry sifting or tumbling ground bud long enough so almost all of the resin is removed and then pressing it long enough with enough heat to form it into a solid. It won't melt and bubble, but it will still be 2, 3 or more times stronger than the bud it came from (depending on how far you push it)...and like with all hashes, you will be inhaling way less tar to get a more intense high.
In my opinion, from purely a health perspective, bud smoking should be widely discouraged and the use and making of hash in it's various forms should be encouraged.
One point to keep in mind when doing this is to not try and separate the sift into different grades before pressing or the less purer grades won't form a solid, but if you keep the sift in one pile with not excessive amounts of contaminant, it will press together and get you higher and healthier. If the result is crumbly and won't form into a hash, then you need to press longer, use more heat and or allow less contaminant it in...it's all a matter of monitoring your progress by press testing small amounts at a time to know when to stop from going too far, after a few times with the same material, you will know when to stop from experience.