Someone mentioned a gas tight seal. That is exactly right but not just for corrosion resistance. Electricity will not flow from one surface to the other unless they are in contact. Gas tight means no gap between the mating surfaces. And in order to achieve that the wire must be deformed. Copper is a good choice because it is ductile.
The ideal mechanical joint is bare wire clamped tight enough to deform the copper strands. The old hifi gear had nice big bolts to facilitate that. The problem is reusing the wire, especially the expensive stuff. Every time the wire is unclamped the ends need to be cut in order to reuse the wire and get a proper gas tight seal. Even the old receivers with the screw terminals were enough to deform the copper strands of the speaker wire. So yes, if you are installing electrical outlets in your house and you use the screw terminals, then you should see the copper wire deform when you tighten down the screws. If not, get a bigger screwdriver.
A properly crimped joint will have less than 5 microOhms resistance. Mechanical cycling of the joint either by temperature cycling or vibration can cause the joint to loosen and resistance to increase. Don't worry, it takes hundreds of thousands to millions of cycles for that to happen on a good joint. If the joint is conveying power it can start to heat up which accelerates the degradation of the joint and thus driving resistance higher which leads to more heating. Bad news.
Spade or bananas on speaker wires is a good compromise for very expensive cables. If the terminations are done properly the degradation to the sound is perhaps zero but the speaker/amp terminals for spades should be stout enough to handle a wrench for tightening.
